JP6461314B2 - Sensor and system for measuring concentration - Google Patents

Description

  The present invention relates to an optical sensor using a solid light source applied to fluid analysis.

  In technical fields, including those applied to the environment, hygiene and industry, it is important to be able to measure the concentration of particle species such as molecules or ions in a fluid. Therefore, there is a great demand for reliable, low-cost, long-life sensor technology that can be used to measure the concentration of chemical species such as chemical molecules and ions in a fluid. is there.

For example, sensors for measuring the concentration of nitrate ions (NO ₃ ⁻ ) in drinking water and wastewater are in great demand. Nitrate ions are suspected to be harmful to humans and animals, and there are limits on the concentration of nitrate ions found in water suitable for drinking. For example, in the United States, nitrogen (NO ₃ ^- -N) concentration of nitrate ions, such as concentration limit is 10 mg / liter (l), the nitrate ion in Europe (NO ₃ ^-) concentration limit of 50 mg / liter It is. It is important to be able to confirm that the concentration of nitrate ions in the drinking water is below these limits. This is especially important when reservoir water, river water, and groundwater can be contaminated by nitrate ions from fertilizers used in agriculture. Wastewater with a high concentration of nitrate ions discharged into the environment can cause oxygen depletion (hypoxia) in the water, which can cause eutrophication such as water bloom and is negative for ecosystems. Influence. There is a limit on the maximum concentration of nitrate ions in the water released to the water circulation. Therefore, there is a great demand for effective nitrate ion sensor technology for analyzing water.

  Growth areas that focus on ion sensing are the aquaculture and hydroponics food industries. In aquaculture, excessive concentrations of ammonium, nitrite or nitrate can adversely affect fish growth and reduce harvest. In hydroponics, the concentration of ions stored in feedstock and supplied to crops, in particular nitrate, phosphate and potassium ions, must be maintained at an optimal level to maximize yield. I must. A currently popular method in both of these industries is to send a sample of water to a laboratory for analysis in order to determine the ion concentration. This means waiting for the analysis to be performed and the results returned, not being able to continue to monitor, and that an immediate adjustment of the ion concentration to the target value is not always possible. Accompanying.

  In the prior art, techniques are known that meet the need for continuous ion monitoring. This technology includes ion selective electrode methods (ISEs) and optical sensors. In the case of nitrate ion sensing, an optical approach is preferred. This is because the ion-selective electrode method requires frequent recalibration in order to receive drift and has a relatively short lifetime.

  Current optical nitrate ion sensors rely on direct absorption of ultraviolet light by nitrate ions, the light having a center wavelength of generally less than 240 nm. The concentration of nitrate ions can be calculated by measuring the light transmitted through the sample. Also, Lambert-Beer's law (A = ε · c · L) is known. Here, A is the absorbance given by the following equation.

ε is the molar extinction coefficient of nitrate ions, c is the concentration of nitrate ions, and L is the path length of the sample. The spectrum of the molar extinction coefficient of nitrate ions is known in the prior art and is displayed in FIG. When the wavelength is greater than approximately 240 nm, the absorbance is very small, and when the wavelength decreases below 240 nm, the absorbance increases rapidly. In order to generate a wavelength of light that is strongly absorbed by nitrate ions (ie, wavelengths less than approximately 240 nm), xenon lamps or deuterium lamps are commonly used in optical nitrate ion sensors in the prior art. Both xenon lamps and deuterium lamps emit in a broad band that includes ultraviolet radiation less than 240 nm (ie, the radiation range includes a range of wavelengths). Other lamps have also been proposed, such as mercury iodide lamps that emit at 206 nm.

  Many features are disclosed in the prior art for improving the accuracy of the measurement of nitrate ion concentration using absorption of ultraviolet light. For example, a reference measurement can be used to determine the intensity of the light source to determine an appropriate value of “initial light intensity” in the Lambert-Beer law equation. Methods for making this measurement include separating the beam to create a reference channel (eg DE4407332C2), expanding the beam so that part of the beam does not pass through the specimen, and either the measurement path or the reference path Can be combined (eg, AT408488B) or reference material can be inserted and removed from the beam path (eg, US3853407A, WO03067228A1).

  Measurement of absorbance by nitrate ions at a plurality of wavelengths is also disclosed in the prior art. For example, DE3324606C2 and JP4109596B2 describe the use of two or more UV wavelengths to determine the reliability of absorbance at wavelengths.

  When the concentration of nitrate ions in a fluid is determined from the absorption of light having a wavelength in the range of 200 nm to 240 nm, the other components in the fluid may have the same light due to unknown amounts (in addition to nitrate ions). The measurement results may not be accurate. By using a second absorbance measurement at a different wavelength, this inaccuracy can be mitigated. As a first example, patent documents including GB2269895B, JP3335776B2 and DE10228929A1 disclose the use of absorbance measurements at wavelengths in the range of 250 nm to 300 nm to correct the absorbance caused by organic molecules. As a second example, DE19902396C2, JP4109596B2 and JP3335776B2 patent documents detail a method of calculating light scattering caused by floating particles. In these documents, transmission at 830 nm, transmission at 633 nm, and direct measurement of light scattering are used, respectively.

  Patent documents DE19902396C2 and AT408488B describe nitrate ion concentration measurement using two different path lengths to improve accuracy. GB2269895B describes the use of variable measurement path lengths. This can be used to obtain a preferred absorbance for a specific nitrate ion concentration. Therefore, the measurable concentration range of the sensor can be expanded. In addition, the patent document JP2000206039A shows that longer wavelengths should be used for absorbance measurements when high concentrations of nitrate ions are present.

  The prior art describes two different detector configurations for nitrate ion sensors. The first configuration is as follows (for example, DE3324606C2). Broadband light from a UV lamp (eg, a xenon lamp or deuterium lamp) propagates through the analyte water. The light propagated through the water is then filtered using a bandpass filter that transmits light having a wavelength range around the center wavelength. The light propagated through the filter is then detected using a photodetector. Bandpass filters for suitable deep ultraviolet wavelengths (200 nm to 240 nm) are relatively poor in performance and expensive. For example, a commercially available filter having a passband of full width at half maximum (FWHM) of 10 nm has a maximum transfer amount of less than 20%. A further disadvantage is that multiple matched filters may be required in that reference and measurement channels that function at the same wavelength are used. The second configuration is as follows (for example, AT408488B). Broadband light from the UV lamp propagates through the specimen water. The light propagating through the water is then detected using a photodetector that measures the spectrum of transmitted light (ie, light intensity as a function of wavelength). This second configuration enables highly accurate nitrate ion concentration measurement, but the configuration of the photodetector is costly.

  The prior art includes nitrate sensor, both an immersion sensor and an in-line sensor. The water immersion sensor supplies water to the sensor by immersing a part or all of the sensor in water that is a specimen to be measured. The in-line sensor is such that water as a specimen is continuously supplied to the sensor, and the water is measured when flowing between the inlet and the outlet.

  The prior art includes devices for optical sensors in other fields (other than for sensing nitrate ions) that use light sources other than xenon and deuterium lamps. Patent application DE102011081317A1 discloses an alternative light source for use in an in-line sensor. One or more solid ultraviolet light sources are held in the housing, emit at a wavelength in the range of 240 nm to 400 nm, and have a FWHM in the range of 10 nm to 20 nm. In order to obtain measurement values, a method of driving a plurality of light sources by sequentially pulsing them is included.

  Another example of using a solid state light source applied to a sensor is patent application US20130015362A1. The patent discloses the use of a frequency doubled laser as a light source for a sensor that detects the presence of particles such as bacteria. Neither DE102011081317A1 nor US20130015362A1 provide a device suitable for measuring the concentration of nitrate ions in water. An optical nitrate ion sensor using a fixed light source cannot be found in the prior art.

DE4407332C2 AT408488B US3853407A WO03067228A1 DE3324606C2 JP4109596B2 GB2269895B JP3335776B2 DE10228929A1 DE19902396C2 GB2269895B JP2000206039A DE102011081317A1 US20130015362A1

  According to one aspect of the present disclosure, a sensor for measuring the concentration of one or more types of ions, molecules, or atoms in a fluid includes a first photodetector that measures the intensity of incident light, and solid-state light emission. A first light source comprising a device, wherein the first light source emits light having a wavelength less than 240 nm (nanometers) incident on the fluid, and the first light detection device passes through the fluid Receive the received light.

  To accomplish the foregoing and related objectives, the invention includes the features fully described below and particularly those set forth in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments according to the invention. These embodiments are exemplary, and some of the various uses in the principles of the present invention may be applied. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.

Prior art optical nitrate ion sensors have several disadvantages. For example, using a deuterium lamp or a xenon lamp filled with a gas complex, the nitrate ion sensor occupies a large capacity (≧ 2,000 cm ³ ) at a high cost, and has a high voltage (≧ 400 V) driving electronic circuit. Requires, high power consumption (between 2W and 7.5W, according to exact source and configuration used), requires warm-up time before measurements are taken, inefficient and costly bandpass filter Will be provided. These disadvantages become a significant barrier when deploying nitrate ion sensing widely.

  There is a longstanding demand for new, low cost sensor technology for measuring the concentration of nitrate ions in water. There has been no significant progress in this field for at least 15 years prior to the present invention. This demand is met by the device according to the invention. This allows for practical use of nitrate sensing in a wider range of applications, including identifying unsafe drinking water (eg, groundwater) at the time of use, broadening environmental measurements, and aquaculture And improve food productivity and waste liquid treatment in hydroponics.

  The apparatus according to the present invention overcomes one or more disadvantages of the prior art and can measure the concentration of ions, molecules or atoms in a fluid. The apparatus according to the present invention includes a solid light emitting member as a light source (for example, a solid light emitting device in the form of a light emitting diode (LED) or a laser diode (LD)) and measures the concentration of ions, molecules, or atoms in a fluid. Therefore, the measurement result of the transmittance of light having a wavelength smaller than 240 nm is used. The apparatus may be used for measuring nitrate ion concentration in water.

During driving, the light of intensity P ₁ emitted from the light source enters the specimen, and the intensity P ₂ of the transmitted light is measured by the light detection means. From the light transmittance P ₂ / P ₁ , it is possible to measure the absorbance of light by ions, molecules, or atoms (hereinafter referred to as “object”), and the concentration of the object is determined using the Lambert-Beer law. Can be determined. Optionally, the intensity P ₁ may be measured by the second light detection means.

  There is a longstanding demand for new, low cost sensor technology for measuring the concentration of nitrate ions in water. There has been no significant progress in this field for at least 15 years prior to the present invention. This demand is met by the device according to the invention. That is, it allows practical use of nitrate ion sensing in wider areas, including the identification of unsafe drinking water (eg, for water drawn from a well) in use, broadens environmental measurements, and aquaculture And improve food productivity and waste liquid treatment in hydroponics.

  By calculating other optical losses of the sensor system, the absorbance of the object can be measured more accurately.

  According to one aspect of the present invention, the wavelength of light emitted from a light source is stable even when operating conditions of the light source are changed in order to improve the reliability of concentration calculation. This aspect of the present invention can be used when the absorption coefficient of the object changes significantly due to a small shift in the wavelength of light emitted from the light source, for example, in the case of a shift between 205 nm and 240 nm for nitrate ions in water. It is particularly effective. This problem occurs because the solid state light emitting device changes the center wavelength of the emitted light depending on the operating conditions (eg, temperature, drive current / voltage). Since the nitric acid sensor in the prior art uses a broadband lamp and a band filter, it is not affected by a change in the wavelength of light used to measure absorbance. However, this inaccuracy can be a serious problem for nitrate ion sensors that use the absorption of light having a wavelength of less than 240 nm emitted by a light source that includes a solid state device. This error in the light source cannot be found in prior art (eg DE102011081317A1) that discloses the use of solid ultraviolet light sources with wavelengths in the range of 240 nm to 400 nm for measuring absorbance.

  In one aspect of the invention, the central wavelength of light emitted from the light source is measured by a direct or indirect method to improve the accuracy of the sensor device. This indicates that an appropriate extinction coefficient ε (λ) is determined and used for concentration calculation, thereby reducing the influence of errors due to changes in the wavelength of the light source.

  In one embodiment of the present invention, the spectral bandwidth of light emitted from the light source is narrow. This makes it possible to provide a highly reliable sensor device that is easy to manufacture and calibrate. If the extinction coefficient of the object changes when the wavelengths of light emitted from the light source are different, an undesirable non-linear dependence of the absorbance on the concentration of the object occurs. This is a problem that arises in particular in sensor devices for measuring the concentration of nitrate ions in water. As long as the bandwidth of the light spectrum is not smaller than 2 nm, the dependence of the absorbance on the concentration of nitrate ions is highly nonlinear. In fact, the linear dependence of absorbance on the concentration of the object is a great advantage. This is because it is not necessary to use an element for correcting non-linearity in order to calculate the concentration of ions, molecules, or atoms of interest in the specimen. Therefore, the sensor calibration process can be simplified and the accuracy can be increased in a wide concentration range.

  An apparatus according to another aspect of the invention uses a light source that includes a solid state light emitting element and one or more frequency conversion elements. The frequency conversion element converts the frequency of light emitted from the solid state light emitting element by, for example, a second harmonic generation process. This device is particularly advantageous when the frequency conversion produces light of a shorter wavelength than that emitted from the solid state light emitting device. In this case, the degree of shift of the center wavelength emitted from the light source caused by the change in the operating condition is smaller than the shift of the center wavelength of the solid state light emitting device. When the frequency conversion element is configured to preferentially frequency convert light in a specific range of wavelengths, the degree of shift of the center wavelength emitted from the light source can be further reduced. By including a frequency conversion element in the light source, the reliability of the device according to the present invention can be improved. The advantages of using a frequency converted light source have not been previously recognized in the prior art and are particularly effective when used in sensor devices that measure the concentration of nitrate ions in water.

  In a further aspect of the invention, one or more auxiliary light sources or second light sources are optionally provided in the sensor device, which are used to transmit light having one or more different wavelengths through the system and the analyte. The rate may be measured. The transmittance of light having one or more auxiliary wavelengths may be used to determine the nature of the analyte or system that may affect the transmittance of light emitted from the first light source. Thereby, the value of the absorbance by the detected object can be made more accurate, and thus the concentration of the obtained object can be made more accurate.

  Devices such as sensor devices according to aspects of the present invention provide significant advantages over the sensor technology described in the prior art, and in particular for sensor technology for measuring nitrate ion concentration in water. .

  Until now, there has not been a sensor for monitoring nitrate ion concentration in water using a solid state light emitting device. The use of solid state light emitters as taught herein provides a significant improvement over prior art sensors. For example, a nitrate ion sensor according to the present invention is lower in cost, smaller in size, increased in robustness, increased in reliability, and reduced in power consumption as compared with a sensor of the prior art.

  In addition, the use of an indicator to control or monitor the wavelength of light generated by a solid state light source disclosed in the present invention is configured to measure the concentration of an object having a large dε (λ) / dλ. It is important in solving the lack of device reliability. This problem has been recognized for the first time in this specification, and it is difficult to measure the concentration of nitrate ions in water because the emission wavelength of a solid state light emitting device is inherently unstable depending on the operating conditions of the device. Is important to the problem. Due to the use of a narrow spectral band solid-state light emitting device (eg, laser diode), the linearity of absorbance dependence on significantly improved concentration further provides higher certainty and more easily made sensors. .

  The advantage of the present invention can be further increased by using the frequency conversion element as the light source for the sensor device. In particular, the unexpected advantage of reducing errors and lack of reliability caused by fluctuations in the wavelength of the solid state light emitting device, and further reducing the spectral bandwidth to make the linearity in the dependence of absorbance on concentration extremely high This is an unexpected advantage. A prior art system for measuring absorbance utilizing particles (US20130015362A1) involves using SHG to provide light for absorbance measurements. However, the sensor device according to this prior art is not suitable for measuring the nitrate ion concentration in water. In particular, the device according to US20130015362A1 does not perform any control over the wavelength of light generated by frequency doubling or the spectral bandwidth of light emission. Both of these features are shown herein to be important aspects of a viable nitrate sensor device.

In the accompanying drawings, the same reference numerals indicate the same configurations or the same features.
FIG. 1 is a diagram showing a molar extinction coefficient spectrum of nitrate ion in water disclosed in the prior art. FIG. 2 illustrates an example of a sensor device according to one embodiment of the present invention. FIG. 3 is a diagram showing an error that occurs in the concentration measurement of nitrate ions due to the shift of the center wavelength of the light emitted from the light source. FIG. 4 is a graph showing the dependence of absorbance on the concentration of nitrate ions in water for light having different spectral bands (center wavelength = 220 nm, path length = 0.25 mm). FIG. 5 is a diagram illustrating an example of a sensor device including a frequency conversion element according to one embodiment of the present invention. FIG. 6 shows the shift of the center wavelength of the light emitted from the solid-state light emitting element in the sensor device (solid line) that does not have the frequency conversion configuration and the sensor device (dotted line) that has the frequency doubling element. It is a figure which shows the comparison of the error which arises in the density | concentration measurement of nitrate ion. FIG. 7 is a diagram showing a comparison of the center wavelengths of light (a) whose frequency is not converted and light (b) whose frequency is doubled in a range of different driving currents. Indicates the direction of increase. FIG. 8 is a diagram showing a comparison of bands of light that has not been frequency-converted and light whose frequency has been doubled. FIG. 9 illustrates an example of a sensor device including an auxiliary light source according to one embodiment of the present invention. FIG. 10 is a diagram showing a timeline of two light sources used in the pulse operation mode. FIG. 11 is a diagram illustrating an example of a sensor device including an auxiliary light source according to an advantageous aspect of the present invention. FIG. 12 is a diagram comparing results obtained using the sensor shown in FIG. 11 (invention) and results obtained from cadmium colorimetric analysis in a sample containing nitrate ions at a concentration of less than 100 mg / litre. It is. FIG. 13 is a diagram comparing results obtained using the sensor shown in FIG. 11 and results obtained from cadmium colorimetric analysis in a sample containing nitrate ions at a concentration higher than 100 mg / litre. FIG. 14 illustrates an example of a sensor device including light scattering measurement according to one embodiment of the present invention. FIG. 15 is a diagram illustrating positions where an exemplary sensor device can be arranged in the drinking water system. FIG. 16 is a diagram illustrating positions where an exemplary sensor device including an automatic density adjusting unit can be arranged. FIGS. 17A and 17B are diagrams showing a position arrangement where the sample processing means can be arranged, in which FIG. 17A shows an inline type and FIG. 17B shows a submerged type. FIG. 18 illustrates an example of a light source according to one embodiment of the present invention. FIG. 19 is a diagram illustrating an example of a sensor device including pump light used to measure the second wavelength according to one embodiment of the present invention. FIG. 20 is a diagram illustrating an example of a sensor device that uses pump light to measure the second wavelength according to one embodiment of the present invention. FIG. 21 is a diagram showing a change in the light intensity output of the pump light Pa and a change in the light intensity output of the light Pb whose frequency is doubled as an effect of the current supplied to the pump wavelength radiating element. It is. FIG. 22 is a diagram comparing the concentration of a solution prepared with known diluted NIST standard nitric acid and the results obtained using the sensor shown in FIG. FIG. 23 is a diagram comparing the results obtained using the sensor shown in FIG. 11 (the present invention) with the results obtained by UV mass spectrometry after adjusting NIST standard nitric acid in a standard laboratory facility. FIG. 24 is a graph showing the dependence of the absorbance on the concentration of nitrate ions in water for light having different spectral bands (center wavelength = 223 nm, path length = 0.75 mm).

  The sensor device according to the present invention can measure the concentration of ions or molecules in a fluid while overcoming the shortcomings of prior art sensors. The sensor device according to the present invention includes a solid-state light emitting component (for example, a light emitting diode (LED) or a laser diode (LD)) as a light source, and uses a measured value of transmittance of light having a wavelength λ of less than 240 nm to Measure the concentration of ions or molecules present in it. The apparatus may be used to measure nitrate ion concentration in water.

An exemplary sensor device according to one aspect of the invention is shown in FIG. The sensor device is configured to measure the concentration of the object 1 in the sample 2. The object 1 may be one or more kinds of ions, molecules, atoms, or any combination thereof. The light source 3 has a solid light emitting element 4 (also referred to as a solid light emitting device), emits light 5 having one or a plurality of wavelengths less than 240 nm, and at least a part of the wavelength is absorbed by the object 1. Part or all of the light 5 emitted from the light source enters the specimen 2 and propagates through the specimen 2. The light incident on the specimen is referred to as a incident light 6 has an intensity P _1. The light propagates the distance L that the specimen has been found. A part of the light is absorbed by an arbitrary object 1 present in the specimen 2. When finished propagated through the specimen 2, the light is called the transmitted light 8 has an intensity P _2. The transmitted light 8 enters the first light detection means 9 and measures the intensity of the transmitted light 8 using the first light detection means 9 (even if the light source 3 and the first light detection means 9 are referred to as a first sensing element). Good). The values of P ₁ and P ₂ may be used to measure the light transmittance (P ₂ / P ₁ ), thereby measuring the absorbance of incident light 6 by the object in the specimen. Then, the concentration of the object in the sample may be calculated from the absorbance. The coupling of light between all members may be performed by free space propagation or by beam shaping means such as a lens.

  Arrange the specimen 2 optionally between two windows 10 and 11 that are substantially transparent at the wavelength of the light 6 (eg, each window transmits at least 10%, preferably at least 50% of the light) The light 6 may be combined to pass through the distance L determined by the specimen. The specimen 2 is a fluid (for example, liquid or gas). For example, the specimen may be water.

The intensity (P ₁ ) of the incident light 6 may be optionally measured using the second light detection means 20. In the measurement, P ₁ is proportional to the intensity of the light incident on the second detection means 20. For example, the intensity of the light 21 emitted from the solid state light emitting device 4 inside the light source 3 may be detected by arranging the second light detection means 20 inside the light source 3. Alternatively, the intensity of the light 5 may be detected by installing the second light detection means 20 outside the light source 3. Optionally, an optical component such as a partial reflection mirror 22 acts on the light 5 (for example, disposed between the light source 3 and the specimen 2), and a part of the light 5 is coupled to the second light detection means 20. (This exemplary configuration is shown in FIG. 2). The advantage of having the second light detection means 20 is that it can be used to identify fluctuations in the intensity of the light 5 emitted by the light source 3, thereby making it possible to more accurately measure the light transmittance.

Alternatively, P ₁ may be measured based on the operating conditions of the light source 3 (eg, current and / or voltage supplied to the light source 3) and the determined dependence of P _{1 on} the operating conditions of the light source 3.

Using the output of the first light detection means 9, the absorbance A of the incident light 6 by the object 1 when the incident light 6 passes through the distance L determined by the specimen 2 is measured. The light transmittance (P ₂ / P ₁ ) depends on the total light loss while light propagates through the sensor device. Examples of light loss include reflection loss and absorption loss at the windows (10, 11), dispersion loss caused by the specimen (eg, due to turbidity), absorption loss within the specimen (eg, absorption by the object, or inside the specimen) Or by absorption by other ions, molecules or atoms). The value of P ₂ / P ₁ may be described as follows.

(1 − TA) is a part of the light absorbed by the object in the specimen, and the absorbance by the object is A = −log ₁₀ (T _A ). (1-T _i ) (i = 1 to n) is part of the light lost by each of the other n factors. For example, the main losses are reflection and absorption by the first window (T ₁ ≈ 0.94), scattering within the specimen (T ₂ ≈ 0.98), absorption by organic molecules in the specimen (T ₃ = 0.90), second In the case of reflection and absorption by a window (T ₄ ≈ 0.95), n = 4, and the following equation holds.

For certain sensor devices, the value of Ti may be known (eg, by a calibration process). Some or all of the Ti values may be determined through a separate measurement means during operation of the sensor device. Therefore, the absorbance A of the object may be determined by measuring the light transmittance (P ₂ / P ₁ ). Using the absorbance A of the object 1 at one or more wavelengths (λ) of the incident light 6, the identified distance L, and the identified molar extinction coefficient ε (λ), the concentration of the object 1 in the sample is measured. Also good.

  The sensor device may optionally include a controller 23 that receives input from the first light detection means 9 and optionally receives input from the second light detection means 20. The controller 23 may measure the absorbance A using these inputs, and may further measure the concentration of the object 1 using an algorithm. For example, the controller 23 may comprise a microcontroller / microprocessor and other electronic circuitry. The controller 23 may further include current generating means for supplying current to an arbitrary part (including the solid light emitting element 4) of the light source 3.

  In one aspect of the present invention, the solid state light emitting device 4 may be one or more LEDs or one or more laser diodes that emit light 21 having a central wavelength of less than 240 nm. The center wavelength of light is preferably larger than 200 nm. Use of a solid state light emitting device has a great advantage over a lamp having a band pass filter used in a sensor of the prior art. For example, increased robustness, increased service life, reduced power consumption, and reduced size.

  Throughout the present disclosure, the numerical value of the wavelength is the numerical value of the wavelength of light propagating through air having a refractive index of about 1. LEDs and laser diodes usually emit light having a wavelength range distributed around the central wavelength. For example, the center wavelength may be equal to the center of the Gaussian function that is most suitable for the emission spectrum of light using the conventional least square error method.

In one aspect of the invention, the center wavelength (λ _c ) of the light 5 emitted by the light source 3 is stabilized against fluctuations in the operating conditions of the light source, for example, whereby λ _c is less than ± 4 nm from the initial value, preferably Will vary by less than ± 2 nm, most preferably by less than ± 1 nm, thereby increasing the reliability of the sensor device. Variations in the operating conditions of the light source include variations in ambient temperature, variations in the temperature of the light source, and / or variations in current and / or voltage supplied to the light source. This aspect of the invention is particularly beneficial for the following sensor devices to perform reliable operations. That is, the extinction coefficient (ε of the object) for a small change in the wavelength of light (for example, a wavelength similar to the wavelength of the “absorption edge” of the extinction coefficient spectrum of the object or the wavelength of the end of the “absorption peak”). (λ)) varies greatly,

A sensor device configured to measure the concentration of such an object. This is particularly important when the object is nitrate ion, the analyte is water, the sensor device is configured to measure the nitrate ion concentration in the water, and the center wavelength is about 205 nm to 240 nm. In this case, dε (λ) / dλ is a large negative value for wavelengths from 205 nm to 240 nm, and is about −200 liters.mol ⁻¹ cm ⁻¹ nm ⁻¹ for wavelengths from 207 nm to 227 nm. For a wavelength of about 220 nm, it becomes a large negative value by overtaking the group of about -664 litres.mol ^-1 cm ^-1 nm ^-1 .

When the center wavelength of the light emitted from the light source 3 is not stable against fluctuations, the extinction coefficient (ε (λ)) used to determine the concentration from the measured absorbance is inappropriate, so that the sensor device Reliability may be reduced. For example, if the light 5 emitted by the light source 3 is predicted to have a center wavelength λ _c , the calculation for determining the concentration from the absorbance assumes ε (λ _c ) as the extinction coefficient (for clarity, In this paragraph, light 5 has a single wavelength λ _c and the band wavelength of light 5 is negligibly small, but generally this is not the case). However, when the light 5 emitted from the light source 3 has the center wavelength λ _c + Δλ because the wavelength of the light emitted from the solid state light emitting device 4 has shifted, the concentration calculation is erroneous. This is because it is more appropriate to use the extinction coefficient ε (λ _c + Δλ). For example, when measuring the nitrate ion concentration in water, FIG. 3 shows the relative error in the measurement of nitrate ion concentration that occurs because the center wavelength is shifted by Δλ from the original 220 nm. The error is large even at small values of | Δλ | <1 nm. The cause of this measurement error does not apply to prior art nitrate ion sensors and has not been recognized so far. Prior art nitrate ion sensors combine a broadband lamp (eg, a xenon lamp or deuterium lamp) with a bandpass filter to provide light having a wavelength of less than 240 nm. The filter transmits a wavelength range of light having a wavelength of less than 240 nm. The wavelength range of light transmitted by these bandpass filters is not significantly affected by changes in operating conditions (for example, changes in ambient temperature). Thus, the prior art nitrate ion sensor is not affected by the shift in wavelength of light used to measure absorbance.

  A solid-state light source may have a large shift in emission wavelength due to changes in operating conditions such as the temperature of the light source, current and / or voltage supplied to the light source. For example, for lasers and LEDs, the normal shift in the center wavelength of light emission is 1 nm / 10 ° C for temperature fluctuations. As a further example, in the case of a change in the current supplied to the light source, the center wavelength of the emission may vary by a few nm over the normal operating current range. Therefore, the sensor is configured to measure the concentration of the object from the transmittance of light having a wavelength of less than 240 nm emitted from the light source 3 including the solid state light emitting element 4, and dε (λ) / dλ of the object is 240 nm. If the sensor shows a large positive value or a large negative value for less than a wavelength, the sensor may be unreliable if the operating conditions of the light source 3 vary.

  Such a lack of reliability is a serious problem for a nitrate ion sensor that uses the transmittance of light having a wavelength of less than 240 nm emitted from the light source 3 including the solid state light emitting device 4.

  The cause of this error has not been found in prior art that describes the use of a solid UV light source with a wavelength of 240 nm to 400 nm for measuring absorbance (eg DE102011081317A1).

In order to solve this problem, in one embodiment of the present invention, the center wavelength of the light 5 emitted from the light source 3 is stabilized against fluctuations in the operating conditions of the light source. According to one aspect of the present invention, this can be realized by one or any combination of the following, but is not limited thereto.
1) Use of the optical wavelength stabilizing element 24. The wavelength stabilizing element 24 reduces the fluctuation of the center wavelength of the light emitted from the solid state light emitting element 4 due to fluctuations in operating conditions. For example, the wavelength stabilizing element returns a part of light emitted from the surface diffraction grating, volume Bragg grating, other diffraction grating, or solid light emitting element 4 to the solid light emitting element 4, and the solid light emitting element 4 emits a specific wavelength. May be a dichroic mirror that preferentially promotes the light emission, thereby reducing the change in the emission wavelength when the operating condition changes compared to the case where there is no wavelength stabilizing element. For example, when the solid-state light emitting element 4 includes a laser diode and the wavelength stabilizing element 24 is a surface diffraction grating, an external resonator type diode laser (for example, Littrow type or Littman Metcalf type) is used by using the surface diffracted photon. May be configured. This is an exemplary configuration schematically shown in FIG. An optical element such as a lens may be disposed between the solid-state light emitting element 4 and the wavelength stabilizing element 24 (this optical element is not shown in FIG. 2). The wavelength stabilizing element 24 does not necessarily have to be disposed between the solid light emitting element 4 and the specimen 2 as in the example of FIG.
2) Use of optional temperature control means 25. The temperature control means 25 keeps the temperature of the solid state light emitting device 4 within a specific range, thereby reducing fluctuations in the wavelength of light emitted from the solid state light emitting device due to changes in operating conditions. For example, the temperature of the solid-state light emitting element 4 may be kept within a specific range of ± 1 ° C. from the center temperature, so that the light emission when the ambient temperature and / or the current supplied to the solid-state light emitting element 4 varies Wavelength variation is reduced as compared with the case where the temperature control means 25 is not provided. The temperature control means 25 may receive a control input from an arbitrary controller 23. The exemplary configuration shown schematically in FIG. 2 includes temperature control means 25.
3) Use of the optical wavelength filter 26. The wavelength filter 26 transmits light having one or more wavelengths within a certain range better than wavelengths outside the range. Therefore, even when the wavelength of light emitted from the solid state light emitting device changes due to a change in operating conditions, fluctuations in the wavelength of light propagated in the filter are reduced. Examples of suitable wavelength filters include bandpass filters, shortpass filters, longpass filters, diffraction gratings, and prisms.

In one aspect of the invention, the center wavelength of the light 5 emitted by the light source 3 is determined by a direct or indirect method, thereby increasing the reliability of the sensor device. This feature of the invention may be used to reduce the effect of the error shown in FIG. Even if the wavelength of light emitted from the solid state light emitting device 4 changes due to a change in operating conditions, if the center wavelength λc is determined, the concentration of the object is determined from the absorbance using an appropriate extinction coefficient ε (λ_c). can do. According to one aspect of the present invention, this can be realized by one or any combination of the following, but is not limited thereto.
1) Use of the optical temperature detection means 27. The temperature detection unit may measure the temperature of the solid state light emitting device 4 or the light source 3. The temperature of the solid light emitting element 4 or the light source 3 may be used as an indirect indicator of the center wavelength of the light emitted from the solid light emitting element 4. For example, the temperature of the solid state light emitting device 4 may be compared with a known change amount or estimated change amount of the emission center wavelength associated with the temperature. For example, the temperature detecting means may be a thermocouple or a thermistor.
2) Use of current detection means. The current detection unit may measure the current supplied to the solid state light emitting device 4. The known value of the current supplied to the solid state light emitting device 4 may be used as an indirect indicator of the center wavelength of the light emitted from the solid state light emitting device 4. For example, the current supplied to the solid state light emitting device 4 may be compared with the known change amount or estimated change amount of the emission center wavelength associated with the current. In order to stabilize the light wavelength, a current regulator and / or voltage regulator may be used to regulate the current and / or voltage supplied to the light emitting device.
3) Measurement of the center wavelength of the light emitted from the solid state light emitting device 4 by a spectrophotometric means (also referred to as a wavelength sensor in this specification).

  Input to any controller 23 by any means for directly or indirectly determining the center wavelength of light, and may be used to increase the accuracy of the concentration of the object determined from the absorbance. For example, the temperature measured by the temperature detection unit may be input to the controller 23.

  In one aspect of the present invention, the light emitted by the light source 3 has a narrow spectral bandwidth (eg, a spectral bandwidth of less than 2 nm, preferably about 1 nm), which is easy to manufacture and easy to calibrate Therefore, a highly reliable sensor device is provided. This aspect of the invention can reliably operate the sensor device configured to measure the concentration of an object such that the light absorption coefficient (ε (λ)) varies greatly with small changes in the wavelength of light. Especially important to make things.

  The spectral bandwidth of light is an indicator of the wavelength range present in the light. In this disclosure, spectral bandwidth is defined as the full width at half maximum (FWHM) of the spectrum of light. For example, the spectral bandwidth is equal to the FWHM of a Gaussian function suitable for the light spectrum using the conventional least square error method.

When the extinction coefficient (ε (λ)) of the object varies for different wavelengths of the incident light 6, the absorbance has an undesirable non-linear dependence on the concentration of the object. The more the extinction coefficient changes within the spectral bandwidth of the incident light 6, the more nonlinear the reaction. This is particularly problematic for sensor devices that are configured to measure nitrate ion concentration in water. In this case, the value of ε (λ) of nitrate ion is between the wavelength of 240 nm and the wavelength of 200 nm, from the value of ε (λ = 240 nm) ≈ 100 liters.mol ⁻¹ .cm ⁻¹ to ε (λ = 200 nm) ≒ 10,000 litres.mol ^-1 .cm ^-1 changes rapidly. In this case, the dependence of the absorbance on the nitrate ion concentration is extremely non-linear unless the spectral bandwidth of the incident light 6 is less than 2 nm. Non-linearity is evident from the plot of FIG. This plot shows the dependence of the absorbance on the nitrate ion concentration in incident light 6 having a center wavelength of 220 nm and spectral bandwidths of 10 nm, 2 nm, 1 nm, and 0.1 nm. This plot shows that in the incident light 6 having a spectral bandwidth of 10 nm, the absorbance has a substantially nonlinear dependence on the nitrate ion concentration. In contrast, the dependence is substantially linear for incident light 6 having a spectral bandwidth of less than 2 nm, especially a spectral bandwidth of 1 nm or 0.1 nm.

  The substantially linear dependence of absorbance on the concentration of the object is a great advantage. This is because no nonlinear correction factor is required to calculate the concentration of a given ion or molecule in the specimen. Thus, the sensor calibration process is simplified and high accuracy can be achieved over a wide concentration range.

  According to the invention, the spectral bandwidth of the incident light 6 used in the sensor device is preferably less than 2 nm. This provides a significant advantage of linearity over prior art sensors (eg, nitrate ion sensors). Preferentially, for example, a solid-state laser such as a semiconductor laser (for example, a laser diode) or an optical pump laser is used as the solid-state light emitting element 4. The use of a laser in this manner provides significant advantages over light sources such as LEDs that have a much larger spectral bandwidth. The use of LEDs or lasers provides significant advantages over the combination of bandpass filters with UV lamps (eg, deuterium lamps or xenon lamps) as found in the prior art. The emission from a laser diode has a very small spectral bandwidth, usually less than 2 nm, and is sometimes referred to as “monochromatic”. This means that the absorption of the laser light by the specimen is substantially linear with respect to the concentration regardless of the extinction coefficient spectrum of the object. In contrast, the emission of an LED typically has a spectral bandwidth of about 10 nm to 20 nm. The emission of a UV lamp (eg, deuterium lamp or xenon lamp) combined with a bandpass filter, as found in prior art sensors, typically has a spectral bandwidth greater than 10 nm.

Another embodiment according to the present invention is shown in FIG. This sensor device shares most or all of several features and advantages with the sensor device described above in connection with FIG. If the components of FIG. 5 are similar or have similar functions to those of FIG. 2, they will be given the same number and will not be described again. According to this aspect of the present invention, the light source 30 includes the solid state light emitting device 4 and one or more frequency conversion devices 31. The light 21 emitted from the solid state light emitting device 4 includes the first center wavelength (Λ _c ). Part or all of the light 21 having the first center wavelength is converted to the second center wavelength (λ _c ) by the frequency conversion element. In a preferred example, the light 21 is frequency doubled by the frequency converting element 31, for example by a second harmonic generation (SHG) process, and the second center wavelength is approximately half the first center wavelength (λ _c ≈Λ _c / 2). The light 32 emitted from the frequency conversion element includes light having a second center wavelength of less than 240 nm. Preferably, light 32 includes light having a second center wavelength greater than 200 nm. In this example, if the frequency conversion includes an SHG process, the light 21 includes light having a first wavelength less than 480 nm, and preferably includes light having a first center wavelength greater than 400 nm. It is out. In the alternative, the light 32 may be converted from the light 21 by other frequency conversions. Other frequency conversions include third harmonic generation (λ _c ≈ Λ _c / 3), fourth harmonic generation (λ _c ≈ Λ _c / 4), and fifth harmonic generation (λ _c ≈ Λ _c / 5), sum frequency generation and difference frequency generation are mentioned, but not limited to these.

  In one example, the solid state light emitting device 4 includes a laser diode. For example, the solid state light emitting device 4 may include a laser diode that emits light having a first center wavelength in the range of 400 nm to 480 nm, preferably in the range of 420 nm to 470 nm. In another example, the solid state light emitting device 4 may be a diode pumped solid state laser including a gain medium of a doped laser crystal.

  Optionally, the light source 30 may further comprise a wavelength stabilizing element 24. This feature is included in FIG. The wavelength stabilizing element 24 can reduce the fluctuation of the wavelength of the light emitted from the solid state light emitting element 4 due to fluctuations in operating conditions. In this way, the wavelength stabilizing element 24 can reduce fluctuations in the wavelength of the light 21 having the first center wavelength (which is “pump” light with respect to the frequency conversion element 31). As a result, the wavelength stabilizing element 24 has an effect of reducing the fluctuation of the frequency converted light having the second center frequency in the light 32. This is because the wavelength of the frequency converted light is determined by the wavelength of the light 21 (for example, in the example of the SHG process of the frequency converting element 31, the wavelength of the light 32 is about half of the wavelength of the light 21). For example, the wavelength stabilizing element returns a part of light emitted from the surface diffraction grating, volume Bragg grating, other diffraction grating, or solid light emitting element 4 to the solid light emitting element 4, and the solid light emitting element 4 emits a specific wavelength. A dichroic mirror that preferentially promotes light emission can be used, thereby reducing fluctuations in the emission wavelength when the operating condition changes compared to the case where there is no wavelength stabilizing element. For example, when the solid-state light emitting element 4 includes a laser diode and the wavelength stabilizing element 24 is a surface diffraction grating, an external resonator type diode laser (for example, Littrow type or Littman Metcalf type) is used by using the surface diffracted photon. May be configured. This is an exemplary configuration schematically shown in FIG. An optical element such as a lens may be disposed between the solid light emitting element 4 and the wavelength stabilizing element 24 (this is not shown in FIG. 5). The wavelength stabilizing element 24 does not necessarily have to be disposed between the solid-state light emitting element 4 and the frequency conversion component 31 as in the example of FIG. Further, the frequency conversion element 31 may be disposed between the solid light emitting element 4 and the wavelength stabilizing element 24. In this latter configuration (not shown in FIG. 5), the portion of the light that is returned to the solid state light emitting element 4 and promotes the light emission of the specific wavelength of the solid state light element preferentially propagates in the frequency conversion element 31. Also good.

  Optionally, the temperature control means 25 may keep the temperature of the solid state light emitting element 4 within a specific range, thereby reducing the fluctuation of the wavelength of light emitted by the solid state light emitting element due to a change in operating conditions. For example, the temperature of the solid state light emitting device 4 is kept within a specific range of ± 1 ° C., whereby the ambient temperature and / or the variation of the wavelength of the light emission when the current supplied to the solid state light emitting device 4 varies is the temperature. This is reduced as compared with the case where there is no control means 25. In this way, the temperature control means can reduce fluctuations in the first and second center wavelengths. The temperature control means 25 may receive a control input from an arbitrary controller 23.

  Optionally, the first center wavelength of the light 21 emitted from the solid state light emitting device 4 and / or the second center wavelength of the frequency converted light is determined in a direct or indirect manner, thereby increasing the reliability of the sensor device. Also good. For example, by using temperature sensing means, current sensing means, or spectrophotometric means in the same manner as described above in connection with the sensor device of FIG. 2 in the detailed description of the invention.

  The light 32 emitted by the frequency conversion element may include light having a second center wavelength and unconverted “pump” or “fundamental” light having a first center wavelength. The filter 33 may be disposed between the frequency conversion element 31 and the sample 2. In FIG. 5, the filter 33 is arranged inside the light source 30, but the filter may be arranged outside the light source. The filter 33 attenuates the intensity of the light having the first center wavelength more than the intensity of the light having the second center wavelength. The filter 33 may include one or more band pass filters. For example, the filter 33 includes one or more mirrors, and the mirror substantially reflects light having the second center wavelength but substantially transmits light having the first center wavelength, and a part of the reflected light or All may appear as light 5 from the filter. It is preferable that the light having the first center wavelength is greatly attenuated by the filter 33. Most of the incident light 6 incident on the specimen is preferably light having the second central wavelength. For example, the incident light 6 incident on the specimen 2 has an intensity of light having the second center wavelength 2.5 times, 10 times, 50 times, 100 times, 500 times that of light having the first center wavelength, Or it may be 1000 times larger.

As described for the sensor device of FIG. 2 (that is, having the light source 3 but not the frequency conversion element 31), the light transmittance (P ₂ / P ₁ ) using incident light 6 incident on the specimen is used. , Thereby determining the absorbance of light by the object, thereby determining the concentration of the object in the specimen.

A sensor device configured to determine the concentration of an object in a specimen from light absorbance includes a light source 30 including a solid light emitting element 4 and one or more frequency conversion elements 31, and incident light incident on the specimen 2. Advantageously, 6 includes frequency converted light. The light 21 having the first center wavelength (Λ _c ) is converted into frequency converted light having the second center wavelength (λ _c ), and the second center wavelength is smaller than the first center wavelength (λ _c <Λ _c ), For example, it is particularly advantageous that λ _c ≈Λ _c / 2.

  The first advantage of having the light source 30 include one or more frequency conversion elements 31 so that the incident light 6 includes frequency converted light is that this sensor device (ie, FIG. 5) includes a solid state light source. Compared to a sensor device (that is, FIG. 2) that measures the concentration of an object in a specimen from the absorbance of light emitted from a light source that does not include a frequency conversion component, the reliability of concentration measurement can be increased. . This advantage is particularly beneficial for a reliable operation of the following sensor device. That is, light absorption by ions or molecules for small changes in the wavelength of light (for example, a wavelength similar to the wavelength at the “absorption edge” of the absorption coefficient spectrum of the object or the wavelength at the end of the “absorption peak”) The coefficient (ε (λ)) varies greatly.

A sensor device configured to measure the concentration of such an object. This is particularly beneficial when the sensor according to the invention is configured to measure nitrate ion concentration in water.

  The first advantage can be understood from FIG. Solid state light sources may exhibit a large shift in emission wavelength due to changes in operating conditions. Some of this behavior has already been detailed. The disadvantageous result caused by the fluctuation of the center wavelength of the incident light 6 incident on the specimen 2 has already been described. That is, since the concentration of the object determined from the absorbance shows a large error with respect to a small change in the center wavelength of the incident light 6, the reliability of the sensor device is reduced. For an example where the sensor device is configured to determine nitrate ion concentration in water, the plot of FIG. 3 shows that a large error is introduced by a slight wavelength shift (Δλ) from the original value. . According to one embodiment of the present invention, the wavelength of light emitted from the solid state light emitting device may be stabilized to reduce fluctuations. However, since the wavelength still varies somewhat, an error occurs in the nitrate ion concentration measured by the sensor device.

When the frequency conversion element 31 is included in the light source 30 so that the second center wavelength (λ _c ) of the frequency converted light is smaller than the first center wavelength (Λ _c ) of the light emitted from the solid state light emitting element 4, The variation of the two center frequencies is smaller than any variation of the first center frequency. For example, if the first center frequency varies by ΔΛ, Λ _c changes to (Λ _c + ΔΛ), and the frequency converted light has the second center wavelength λ _c ≈Λ _c / n, the second center The variation in wavelength is Δλ≈ΔΛ / n, and λ _c changes to (λ _c + Δλ). For example, when the frequency conversion is an SHG process and n = 2, the variation of the second center frequency is about half of the variation of the first center frequency.

In another aspect of the present invention, when the frequency conversion element 31 is configured to preferentially frequency convert light having a wavelength in a specific range, the variation of the second center wavelength can be further reduced (for example, the frequency If the conversion is an SHG process, it can be reduced to less than half of the variation of the first center wavelength). This is a further advantage of including a frequency conversion element 31 in the light source 30 of the sensor device. The frequency conversion element 31 may be configured such that a substantial amount of the frequency converted light 32 is produced having only a wavelength substantially between λ ₁ and λ ₂ (λ ₁ <λ ₂ ). For example, the frequency-converted light is between the lambda ₂ wavelength from lambda ₁ is at least the maximum intensity of the resulting frequency converted light to the wavelength of between the (lambda ₁ -0.5 nm) and (λ ₂ + 0.5nm) The frequency conversion element may be configured to have an intensity of 1%, preferably at least 10%, and to reduce the intensity at wavelengths outside this range. In this case, the sensor device operates under the condition that the incident light 6 incident on the specimen is always in the range between λ ₁ and λ ₂ , so that regardless of the operating conditions of the light source, Gives high reliability to the appropriate extinction coefficient. The value of (λ ₂ -λ ₁ ) may be less than 2 nm, less than 1 nm, less than 0.5 nm, or less than 0.1 nm. The value of (λ ₂ -λ ₁ ) is preferably small.

For example, if the frequency converting element 31 provides an SHG process, a significant amount of light that is doubled in frequency has a wavelength in the range between Λ ₁ and Λ ₂ (where Λ ₁ <Λ ₂ ). You may comprise a frequency conversion element so that it may arise only from the light 21. FIG. Light having these wavelengths, the SHG process, is converted into light having about λ ₁ ≒ Λ _1/2 and λ ₂ ≒ Λ _2/2 of the wavelength. Therefore, even when the first center wavelength of the light 21 varies significantly higher than the significantly lower value or lambda ₂ than lambda _1, the center wavelength of the frequency converted light λ ₁ ≒ Λ _1/2 and lambda ₂ ≒ It does not change much except in the range of between the Λ _2/2.

One way to configure the frequency conversion element to have the appropriate λ ₁ and λ ₂ is that the frequency conversion process is “phase matched” for the generation of frequency converted light having a wavelength of λ <λ ₁ or λ> λ _2. It is not to be done. “Phase matching” is a state in which, in the frequency conversion process, the light wave of the pump light and the frequency converted light are substantially in phase with each other when propagating in the frequency conversion element. If the frequency conversion process is not in phase, the intensity of the frequency converted light is very low (eg, less than 10% or less than 1% of the intensity obtained when the frequency conversion process is phase matched).

In accordance with one aspect of the present invention, the wavelength range (eg, the values of λ ₁ and λ ₂ ) in which the frequency conversion is phase matched is controlled in various ways to provide appropriate λ ₁ and λ ₂ or appropriate (λ ₂ -λ ₁ ) may be obtained. In a first example of an appropriate method, the intensity of the focusing of the pump light incident on the frequency conversion element is selected to obtain an appropriate value of λ ₁ and λ ₂ or an appropriate (λ ₂ −λ ₁ ). Also good. If the pump light is a collimated collimated beam or is loosely focused on one or both sides of the beam (ie, if the pump light has a small convergence angle on one or both sides), then (λ ₂ -λ ₁ ) may be smaller than (λ ₂ −λ ₁ ) obtained when the pump light is tightly focused (ie, when the convergence angle of the pump light on one or both sides is larger). In a second example of a suitable method, the direction of the pump light through the frequency conversion element is selected to determine a suitable λ ₁ and λ ₂ or a suitable (λ ₂ -λ ₁ ) value. This is particularly suitable for frequency conversion elements in which phase matching is obtained by so-called “birefringence phase matching”. In a third example of a suitable method, the structure of the frequency conversion element is selected to determine a suitable λ ₁ and λ ₂ or a suitable (λ ₂ -λ ₁ ) value. For example, when the length of the frequency conversion element is increased (that is, the length measured parallel to the direction of the pump light), the value of (λ ₂ −λ ₁ ) can be reduced.

An example of such a beneficial effect of including a frequency conversion element in the light source 30 is plotted in FIG. FIG. 7A shows an emission spectrum from the solid state light emitting device 4 in the light source 30. The solid state light emitting device 4 had a laser diode containing an Al _y In _x Ga _1-xy N semiconductor material.

The temperature control means 25 was applied to the solid state light emitting device 4, and the temperature of the package including the laser diode was maintained at 25 ° C. ± 0.1 ° C. Sixteen spectra are plotted with vertical offsets between each data. Each spectrum was obtained by supplying a higher current to the laser diode than the spectrum below it. Although the temperature control means 25 was provided, it is clear that the center wavelength of the light emitted from the laser diode has greatly changed as the current supplied to the laser diode increases. For example, the center wavelength of the bottom spectrum (minimum current) is about 438.4 nm, the center wavelength of the top spectrum (maximum current) is about 441.0 nm, which corresponds to a value of ΔΛ≈2.6 nm. The arrow indicates the direction in which the current supplied to the laser increases and indicates the approximate trend of the center wavelength of the light. The light source 30 further includes a frequency conversion element 31. The frequency conversion element 31 included a β-BaB ₂ O ₄ crystal configured to provide a phase matching type I SHG of the light emitted by the laser diode. FIG. 7B shows a spectrum of the frequency converted light generated by the frequency conversion element 31 corresponding to the spectrum of FIG. It is clear that the fluctuation of the center wavelength of light in FIG. 7B is extremely small compared to the fluctuation in FIG. For example, the center wavelength of the lower end spectrum (minimum current) is about 219.3 nm, the center wavelength of the upper end spectrum (maximum current) is about 220.3 nm, which corresponds to a value of Δλ≈1.0 nm. The reasonably small fluctuation of the wavelength of the frequency-converted light is due to the effect of frequency conversion (Δλ ≒ ΔΛ / n, n = 2 in this example), and in this configuration, this specific frequency conversion This is because the element preferentially converts light having a wavelength of about 440 nm into light having a wavelength of about 220 nm (more specifically, Λ ₁ ≈ 439 nm and Λ ₂ ≈ 441 nm; that is, λ ₁ ≈ 219.5 nm and λ ₂ ≒ 220.5 nm). It is particularly advantageous to use a frequency conversion element 31 containing a β-BaB ₂ O ₄ crystal. This is because such a frequency conversion element is configured to give a small value of (λ ₂ -λ ₁ ) by phase matching of the SHG process, and the temperature of the β-BaB ₂ O ₄ crystal changes due to changes in operating conditions. Even so, the values of λ ₁ and λ ₂ for the chosen configuration do not vary much.

  By providing the incident light 6 incident on the specimen 2 using frequency conversion, it is possible to prevent the reliability of the light from being reduced due to a change in the center wavelength of the light emitted from the solid state light emitting device due to a change in operating conditions.

  Therefore, providing the frequency conversion element increases the reliability of the sensor device according to the present invention. In particular, the reliability when the operating conditions such as the ambient temperature of the sensor device fluctuate increases. This advantage of using a frequency converted light source has not previously been recognized in the prior art and is particularly beneficial when used in sensor devices configured to measure nitrate ion concentration in water.

  For an embodiment in which the sensor device is configured to measure nitrate ion concentration in water and the frequency conversion in the frequency conversion element 31 is an SHG process (ie, n = 2), the improvement according to this aspect of the present invention is illustrated. 6 can be seen. FIG. 6 shows the dependence of the nitrate ion concentration error on the wavelength shift of the solid state light emitting element 4 with respect to the solid state light emitting element 4 of the light source 3 not performing frequency conversion (the solid state light emitting element wavelength shift = Δλ; solid line), This shows each of the solid-state light-emitting elements 4 (wavelength shift of the solid-state light-emitting elements = ΔΛ; broken line) of the light source 3 including the frequency conversion element 31. In FIG. 6, Δλ is half of ΔΛ due to the frequency conversion element. The error in the nitrate ion concentration is approximately halved by providing the frequency conversion element including the SHG process.

  A second advantage of the configuration in which the light source 30 includes one or more frequency conversion elements 31 and the incident light 6 includes frequency conversion light is that the light source 30 has a second central wavelength with a small spectral bandwidth. It is the point which provides the light which has. This second advantage of using a frequency converted light source has not been recognized in the prior art. As can be seen from the above description and FIG. 4, this is advantageous because the dependence of the absorbance on the concentration of the object (nitrate ions in the example of FIG. 4) is substantially linear, which makes it easier to manufacture. This is because a sensor device that is easy to calibrate and has high reliability can be provided.

The first aspect of the above advantages will be described below. When the spectral bandwidth of light having the first central wavelength (Λ _c ) emitted from the solid state light emitting device 4 is b ₁ (measured in units of wavelength nm), the spectral bandwidth of the light is Λ _min ≈Λ _c the -b _1/2 and _{Λ max ≒ Λ c + b 1} /2 wavelengths during the. When the frequency conversion is an SHG process, light having these wavelengths is converted to frequency converted light having a second central wavelength λ _c and a spectral bandwidth of about b ₂ as follows.

Thus, a b ₂ ~ b _1/2, the spectral bandwidth of the frequency converted light is significantly smaller than the spectral bandwidth of the light emitted in the solid state light emitting terminals. In general, in the frequency conversion element 31 that generates the frequency conversion light having the second center wavelength smaller than the first center wavelength of the light emitted from the solid state light emitting element 4, the spectral bandwidth of the light having the second center wavelength is , Lower than the spectral bandwidth of the light having the first central wavelength.

The second aspect of the above advantage is that the spectrum bandwidth of the light 21 can be further reduced by the frequency conversion element 31 if the frequency conversion element is configured to preferentially frequency convert light having a wavelength in a specific range. It is. As described above, the frequency conversion element 31 may be configured to generate a significant amount of frequency converted light so as to have only a wavelength between λ ₁ and λ ₂ . For example, a frequency conversion element that provides an SHG process may be configured such that a significant amount of frequency converted light only originates from light 21 having a wavelength in the range of Λ ₁ to Λ ₂ . Light having these wavelengths, when converted by the SHG process, a frequency converted light having about λ ₁ ≒ Λ _1/2 and λ ₂ ≒ Λ _2/2 of the wavelength. Therefore, even if the spectral bandwidth of the light 21 having the first central wavelength is significantly larger than Λ ₂ −Λ ₁ , the spectral bandwidth of the light 32 having the second central wavelength is significantly larger than λ ₂ −λ _1. Don't get big.

A third aspect of the above advantage is that the spectral bandwidth of the light 21 can be further reduced by the frequency conversion element 31. This is because the frequency conversion efficiency of an arbitrary frequency depends on the intensity of light of that wavelength. This is true when the frequency conversion process includes a nonlinear optical process such as SHG. In the case of SHG, for example, the wavelength of light with high intensity (eg, near the center wavelength Λ _G of the Gaussian-like spectral peak) is the wavelength of light with low intensity (eg, Λ _G + b _G / 2 or Λ _G -b in _G / 2, b _G can than the spectral bandwidth) of the Gaussian-like spectral peaks, converted efficiently. As a result, the spectral bandwidth of the frequency converted light can be further reduced as compared with the spectral bandwidth of the light emitted from the solid state light source 4.

An example of such a beneficial effect by providing the light source 30 with a frequency-doubling element is plotted in FIG. FIG. 8A shows an emission spectrum from the solid state light emitting device 4 in the light source 30 (this is the same as the light source described above with reference to FIG. 7). FIG. 8B shows an emission spectrum of the light generated by the frequency conversion element 31. Let b ₁ and b ₂ be approximate spectral bandwidths. The band of light generated by the frequency conversion element (b ₂ ≈0.4 nm) is significantly narrower than the band of light emitted by the solid state light emitting element (b ₁ ≈1.2 nm). In this case, the laser emitted light having a wavelength of about 440 nm, but the band is typical for laser diode emission at many visible and ultraviolet wavelengths.

  In a further aspect of the invention, one or more auxiliary light sources are optionally provided in the sensor device, which can be used to measure the transmission of light having one or more different wavelengths through the system and the analyte. Good. These auxiliary light sources may emit light having any wavelength, including wavelengths greater than 240 nm. Using the measured transmittance of the light emitted from the one or more auxiliary light sources, the concentration of the object 1 is such that the incident light 6 passing through the specimen (that is, part or all of the light emitted from the light source 3 or 30). ) May be improved in accuracy when determined from the measured transmittance. A sensor device with one auxiliary light source 40 is shown in FIG. The sensor device shown in FIG. 9 has some features in common with the sensor device shown in FIG. Features common to the two sensor devices are given the same numbers in the following description and will not be described again. In the preferred embodiment, the light source 40 comprises a solid state light emitting device 41, such as an LED or a laser diode. The light source 40 emits light having a first auxiliary center wavelength. The light source 40 may include a temperature control unit 42 and / or a temperature detection unit 43.

  Part or all of the light having the first auxiliary center wavelength emitted from the auxiliary light source 40 enters the specimen 2 as incident light 49. The light propagates through the specimen and the arbitrary windows 10 and 11, and the intensity of the transmitted light is determined by the third light detection means 46. The intensity of the incident light 49 may be determined, optionally via an optical element such as a partial reflection mirror 48, using fourth light detection means 47 that receives light intensity proportional to the intensity of the incident light 49. . A combination of the third light detection means 46 and the auxiliary light source 40 is also described herein as an auxiliary detection element.

For example, the transmittance of light having one or more auxiliary wavelengths may be used to determine the nature of the analyte or system that may affect the transmittance of incident light 6. Such properties include turbidity of the analyte (light scattering), concentration of other ions or molecules (eg, organic molecules) in the analyte, or cleanliness of windows 10 and / or 11 (ie, one or more Ti _). To determine the value of). Then, the concentration of the target 1 may be determined more accurately by using this data to calculate the absorbance value of the target 1 in the sample 2 more accurately. The above data may be used to determine a second property of the analyte, which may be output as a sensor result (eg, concentration of ions or molecules other than the object in the analyte). . Any number of auxiliary light sources may be provided.

For example, if the sensor device is configured to measure nitric acid concentration in water, a first auxiliary light source having a first auxiliary central wavelength of 250 nm to 1000 nm (preferably 250 nm to 700 nm) is used. It may be provided. By using the measured transmittance of light having the first auxiliary center wavelength, the accuracy in determining the absorbance due to nitrate ions from the transmittance (P ₂ / P ₁ ) of the incident light 6 may be increased. This takes into account phenomena such as light absorption in the contaminant layer formed in one or both of the windows 10 and 11, light scattering due to the turbidity of the specimen 2, and light absorption by organic molecules in the specimen 2. May include.

In another example, a first auxiliary light source having a first auxiliary center wavelength between 200 nm and 240 nm may be provided. Using the measured transmittance of light having the first auxiliary center wavelength to determine the absorbance due to nitrate ions in consideration of the absorbance due to nitrous acid (NO ₂ ⁻ ) in the specimen 2 from the transmittance of incident light 6 The accuracy of the may be increased.

  The wavelength of the light 5 emitted from the light source 3 or the light source 30 and the length 7 of the optical path passing through the specimen 2 may be selected so that the absorbance by the object is preferably more than 0.05 and less than 2.

  Preferably, the absorbance is 2 or less. This is because if this value is exceeded, the increase in absorbance with concentration may become very non-linear due to the overlap of absorption cross-sections, which may reduce the accuracy of the measurement. More preferably, the absorbance is 1.5 or less. Therefore, the optimum optical path length L and wavelength of the light 5 may be selected so that the absorbance is about 1.5 with respect to the maximum concentration of the object to be analyzed by the sensor device.

  Additional considerations such as the minimum gas concentration of the object and the minimum or maximum desired optical path length can be used to further identify an appropriate combination of wavelength and optical path length.

As an example, consider a sensor device that is used to determine whether it is safe to drink by measuring the nitrate concentration of water intended for human consumption. The upper limit of the maximum safe concentration of nitrate ion in drinking water determined by the World Health Organization (WHO) is 50 mg / litre NO ₃ , so the sensor device can be used from 0 mg / litre NO ₃ ^- to 100 mg / litre NO ₃ ^- is expected to produce accurate measurements in the range. In view of practical considerations such as low resistance to water flow, easy cleaning of windows, while maintaining compactness, the optical path length is preferably L = 5 mm. If the optical path length is L = 5 mm, an appropriate wavelength can be estimated using the Lambert-Beer law and the known wavelength dependence of the absorption coefficient of nitrate ions in water. In this case, a suitable wavelength has an extinction coefficient ε such that A = ε.cL≈1.5 when c = 100 mg / litre and L = 5 mm. Therefore, a suitable choice for the sensor device is a center wavelength of about 225 nm.

  In the specific concentration range, there are various options suitable for the optical path length and wavelength. The above example assumes light 5 with a spectral bandwidth of less than 2 nm. If the light 5 has a larger spectral bandwidth, the effect of the spectral bandwidth on the overall extinction coefficient for the light 5 may be considered.

  The sensor device according to aspects of the present invention provides significant advantages over the sensor technology described in the prior art, particularly for sensor technology for measuring nitrate ion concentration in water.

  Until now, there has not been a sensor for monitoring nitrate ion concentration in water using a solid state light emitting device. The use of solid state light emitters as taught herein provides a significant improvement over prior art sensors that use a combination of a UV lamp (eg, a xenon lamp or deuterium lamp) and a bandpass filter. For example, a nitrate ion sensor according to the present invention is lower in cost, smaller in size, increased in robustness, increased in reliability, and reduced in power consumption as compared with a sensor of the prior art. Further, using the indicator to control or monitor the wavelength of the light generated by the solid state light source disclosed in the present invention is such that dε (λ) / dλ is a large positive value or a large negative value. This is important in resolving the lack of reliability of sensor devices that are configured to measure the concentration of water. This problem has been recognized for the first time in this specification, and it is difficult to measure the concentration of nitrate ions in water because the emission wavelength of a solid state light emitting device is inherently unstable depending on the operating conditions of the device. It is important for the difficult problem. By using a solid state light emitting device (eg, a laser diode) with a narrow spectral bandwidth, the linearity of absorbance dependence on concentration is greatly improved, thereby further providing a more accurate and easier to manufacture sensor. be able to.

  By using the frequency conversion element as the light source for the sensor device, the advantages of the present invention can be further increased. Among other things, the unexpected advantage of reducing errors and lack of reliability caused by fluctuations in the wavelength of the solid state light emitting device, and further reducing the spectral bandwidth to make the linearity of the absorbance dependence on concentration extremely high This is an unexpected advantage. A prior art system for measuring absorbance using particles (US20130015362A1) involves using SHG to provide light for absorbance measurement. However, the sensor device according to this prior art is not suitable for measuring the nitrate ion concentration in water. In particular, the device according to US20130015362A1 does not perform any control over the wavelength of light generated by frequency doubling or the spectral bandwidth of light emission. Both of these features are shown herein to be important aspects of a viable nitrate sensor device.

  New low-cost sensor technology for measuring nitrate ion concentration in water has been sought for many years. Prior to the present invention, there has been no significant progress in the art for at least fifteen years. The present invention meets this demand and makes it possible to put nitrate ion detection into practical use in a wider range of applications. Such uses include identifying unsafe drinking water at the site of use (for example, for well water or city water treatment facilities), extensive environmental monitoring, and productivity in aquaculture and hydroponic food production. Improvement and wastewater treatment.

1st Example The 1st Example of this invention is a sensor apparatus for detecting the density | concentration of the nitrate ion in drinking water. The sensor device uses a solid light emitting element that emits light having a wavelength of less than 240 nm. The sensor device is configured to measure NO ₃ ⁻ up to 50 mg / litre.

  A schematic diagram of the sensor device is shown in FIG. The sensor device includes a light source 3, a sample 2, and a sample processing unit 12 (also referred to as sample processing unit). The light source 3 includes a solid light emitting element 4 that emits light 21. The sample processing means 12 includes a first window 10 and a second window 11. All or part of the light 21 is emitted from the light source 3 as the emitted light 5. All or part of the light 5 enters the first window 10 as incident light 6. Incident light 6 propagates through the first window 10, the specimen 2, and the second window 11. The transmitted light 8 enters the first light detection means 9. The first window 10 and the second window 11 are almost transparent to the light 6. The sensor device may include a partial reflection mirror 22. The partial reflection mirror 22 reflects a part of the light 5 and directs the second light detection means 20 additionally provided with a part of the light 5. The controller 23 receives an input from the first light detection means 9. The controller 23 may receive an input from the second light detection means 20. The controller 23 controls the operation of the light source 3.

The solid state light emitting device 4 may be an LED that emits light having a central wavelength of 200 nm to 240 nm. For example, an LED including Al _y Ga _1-y N (0 ≦ y ≦ 1) semiconductor material emits light having a central wavelength of about 210 nm to 240 nm. Preferably, the LED is provided between a p-doped Al _a Ga _1-a N layer (0 ≦ a ≦ 1) and an n-doped Al _b Ga _1-b N layer (0 ≦ b ≦ 1). A light emitting region including the Al _y Ga _1-y N layer (0.6 ≦ y ≦ 1). In another example, the solid state light emitting device 4 may include boron nitride or Al _c Ga _d B _1-cd N (0 ≦ c ≦ 1; 0 ≦ d ≦ 1). As another example of the first embodiment, the solid state light emitting device 4 includes an Al _y Ga _1-y N semiconductor material that emits light 21 having a center wavelength of about 225 nm. The light intensity PO of light emitted from the light source is preferably greater than 10 μm. Otherwise, it is necessary to increase the sensitivity of the first light detection means. In this example, the light source 3 does not include the wavelength stabilizing element 24 or the filter 26 shown in FIG.

  The first window 10 and the second window 11 preferably have a transmittance of 10% to 100% with respect to the incident light 6 (in this example, the wavelength is about 225 nm). The first window 10 and the second window 11 may include UV fused silica (UVFS). UV fused silica has a transmittance of 90% or more at a wavelength λ = 225 nm. Other suitable materials for the first window 10 and the second window 11 include quartz, polytetrafluoroethylene (PTFE), fluoropolymer, fluorinated ethylene propylene (FEP), CYTOP, and polymethyl methacrylate (PMMA). Is included. Incident light 6 passes substantially perpendicular to the first window 10 and the second window 11. The distance L of light propagating in the specimen 2 is 0.1 mm to 100 mm, preferably 0.5 mm to 20 mm, and most preferably about 1 mm to about 10 mm. The sample processing means 12 has a sample inlet and a sample outlet, and a first window 10 and a second window 11 are provided between the sample inlet and the sample outlet. This provides a continuous flow of analyte that passes through the light propagating between the first window 10 and the second window 11, providing the series sensor shown in FIG. 17 (a). For example, the specimen processing means 12 may be a tube (for example, PVC or other polymer, or stainless steel or other alloy) provided with a first window 10 and a second window 11. Alternatively, an immersion sensor shown in FIG. 17B may be used as the sample processing unit 12.

Incident light 6 enters the first window 10 with a light intensity P ₁ . Transmitted light 8 is incident at a light intensity P ₂ to the first light detecting means 9. The light detection means may include a photodiode that generates an electrical signal proportional to the incident light. For example, the first light detection means 9 may include a silicon-based photodiode, an Al _y Ga _1-y N-based photodiode (0 ≦ y ≦ 1), or a GaP-based photodiode. Alternatively, the first light detection means 9 may include a silicon-based avalanche diode, a photomultiplier tube, or a micro photomultiplier tube. The photodiode may be configured as an electric circuit such that a potential difference generated by the photodiode in response to absorbed light is monitored as an output. In another example, the photodiode may be configured as an electric circuit so that a current value generated by the photodiode in response to absorbed light is monitored as an output. The output is input to the controller 23 by wireless means or wired means. The controller 23 includes a microcontroller or a microprocessor.

Next, the controller 23 determines the nitrate ion concentration in the sample 2 using the input from the first light detection means 9. An example of a suitable calculation method is as follows. In the calibration process, an analyte having a known nitrate ion concentration (preferably deionized water having a nitrate ion concentration of 0) is measured. In this measurement, the light intensity of the transmitted light 8 detected by the first light detection means 9 is P ₂ ′. Next, it was detected by the second light detection means according to Beer-Lambert's law, a known constant ε (in the case of nitrate ion for wavelength 225 nm, ≈1870 litres.mol-1, cm-1) and L (10 mm) Based on the light intensity P ₂ , the nitrate ion concentration of the unknown specimen is calculated.

This calculation is executed by the controller 23 using the stored ε value and P ₂ 'value. These ε values and P ₂ ′ values are suitability values of the individual sensor devices. The above calibration steps may be performed only once for a typical device, and the calibration results apply to similar sensors. The calibration step may be performed when the sensor is used for the first time on an unknown analyte. Alternatively, the calibration step may be performed as many times as desired.

  LEDs typically emit light with a spectral bandwidth of 10 nm to 20 nm. As a result, the sensor device described above has a non-linear absorbance response with respect to the concentration (FIG. 4). Therefore, the use of a calibration process is advantageous when the sensor device is used to measure a plurality of reference samples having nitrate ion concentrations that cover at least the range in which the sensor device operates. The approximate mathematical dependence of nitrate ion concentration on absorbance is then determined and used to improve the calculation. The calculation is executed by the controller 23, for example. Subsequently, the nitrate ion concentration in the specimen 2 is calculated from C = f (A). f () is the mathematical dependence of concentration on absorbance. The calibration curve is also estimated from the known spectrum of the light emitted from the light source 3 and the known variables for the absorbance coefficient of nitrate ions at the wavelength ε (λ).

Alternatively, a partial reflection mirror 22 may be provided between the light source 3 and the sample processing means 12. The partial reflection mirror 22 has a reflectance of 1% to 70% with respect to light having a wavelength of 225 nm. The partial reflection mirror 22 preferably has a reflectance of 10% to 50% with respect to light having a wavelength of 225 nm. The light reflected by the partial reflection mirror 22 enters the second light detection means 20. The light intensity of the light transmitted through the partial reflection mirror 22 is preferably 50% to 90% of the light intensity of the light incident on the partial reflection mirror 22. Let P _{1 be} the light intensity of the light transmitted through the partial reflection mirror 22, and PR be the light intensity of the light reflected by the partial reflection mirror 22 (see FIG. 2). The first light detection means 9 and the second light detection means 20 may be photodiodes that generate an electrical signal proportional to the incident light. For example, it is a silicon-based photodiode (a design similar to the first photodetection means 9 is considered). The P ₁ / P _R value is constant and therefore the measured PR is used to measure and grasp the variation in the light intensity of the incident light 6. The above-described variation in the light intensity of the incident light 6 is caused by a variation in the light intensity of the light emitted from the light source 3 in calculating the absorbance by the object. For example, when the specimen is deionized water having a nitrate ion concentration of 0, the light intensity of light incident on the second light detection means 20 is PR ′, and the light intensity of light incident on the first light detection means 9 is P ₂ '. Next, the nitrate ion concentration in the unknown specimen 2 is calculated based on the following equation. This equation explains the fluctuation of the light intensity in the light source 3.

The above calculation is executed by the controller 23. The multiple calibration sample method described in detail here is also used in combination with the partially reflective mirror 22 and the photodiode 20 using this highly accurate absorbance value.

  Further, the sensor device may include means for stabilizing the wavelength of light emitted from the light source 3. This configuration can be realized by additionally using a temperature control element 25 that is in thermal contact with the solid state light emitting element 4. The temperature control element 25 operates so that the temperature of the solid state light emitting element 4 is maintained within a predetermined range over the entire range of expected operating conditions (for example, ± 1 ° C.). Thereby, the fluctuation | variation of the wavelength of the light radiated | emitted from the solid light emitting element 4 is suppressed. The temperature control element may be a Peltier member. This Peltier member has one surface in thermal contact with the solid state light emitting device 4 and the other surface in thermal contact with the heat sink. Thereby, the solid light emitting element 4 and the heat sink are substantially thermally separated from each other except through the Peltier member. In other examples, the temperature control element is a fan or liquid heat exchange member (eg, to move heat toward or away from the solid state light emitting element 4 to maintain a stable temperature). The flow of the specimen is used. Alternatively, the temperature detecting means 27 and the solid light emitting element 4 may be brought into thermal contact. The controller 23 uses the output from the temperature detection means 27 to determine the exact operating condition of the Peltier member. Thereby, the temperature of the solid state light emitting device 4 is maintained within a predetermined range. In another example, another electrical circuit (eg, a PID circuit) uses the output of the temperature sensing means to determine the exact operating condition of the Peltier member. The temperature detection means may be a thermistor, a thermocouple, or a semiconductor temperature sensor.

  When the sensor device includes the temperature detection means 27, the center wavelength of the light emitted by the solid state light emitting device 4 is indirectly estimated using the temperature control means 25 or without using the temperature control means 25. In order to do so, the temperature of the solid state light emitting device 4 or the light source 3 may be used. For example, the temperature dependence (known) of the wavelength of the light emitted from the solid state light emitting device 4 may be used to accurately estimate the appropriate absorbance coefficient used in the calculation, whereby the concentration of nitrate ions is determined from the absorbance. Is done.

  Alternatively, the sensor device is configured such that no ambient light or almost no ambient light is incident on the first light detection means 9 and / or the second light detection means 20. The ambient light is light other than the light emitted from the light source 3. The light intensity of the ambient light incident on the first light detection means 9 or the second light detection means 20 is the light intensity emitted by the light source 3 incident on the first light detection means 9 and the second light detection means 20. It is preferably less than 10% of the light intensity. The light intensity of the ambient light incident on the first light detection means 9 or the second light detection means 20 is emitted by the light source 3 incident on the first light detection means 9 and the second light detection means 20. Most preferably, it is less than 1% of the light intensity. The sensor device may include a shield that prevents ambient light from entering the first light detection means 9 or the second light detection means 20. The first window 10 and the second window 11 are preferably enclosed. For example, the first window 10 and the second window 11 are enclosed by a tube, and environmental light is effectively blocked. The sensor device therefore does not require a bandpass filter for limiting the incidence of light of a certain wavelength on the first light detection means 9 or the second light detection means 20.

  In the first embodiment described above, an optical component (for example, a lens) for shaping a light beam is not used when all members of the sensor are connected by light. However, a configuration in which one or more optical components are arranged on any one of the light beam paths is also evaluated for the purpose of changing the light propagation in order to improve the performance of the sensor device.

Second Embodiment A second embodiment of the present invention is the same as the first embodiment except that the solid state light emitting device 4 includes a laser. Many of the configurations are the same as those of the first embodiment, and their description will not be repeated. A second embodiment is described in FIG.

The solid-state light emitting element 4 is an optically pumped laser having a laser diode containing an Al _y Ga _1-y N material (0 ≦ y ≦ 1) or an Al _y Ga _1-y N (0 ≦ y ≦ 1) semiconductor material. Good. As another example of the second embodiment, the solid state light emitting device 4 is a laser diode including an Al _y Ga _1-y N semiconductor material that emits light 21 having a central wavelength of about 225 nm.

  It is preferable to select a laser as the solid state light emitting element 4 in the light source 3. The reason is that the laser (1) emits light in a narrower frequency band, (2) provides light of a more stable wavelength to change than the LED, (3) provides light of approximately linear polarization (4) The quality of the light beam is high, and parallel light can be easily formed.

  The spectral bandwidth of the light 5 emitted by the light source 3 is less than 2 nm, preferably about 1 nm. If the spectral bandwidth is narrow, the absorbance is almost linearly dependent on the nitrate ion concentration in the sample. This increases the reliability of the sensor device, reduces the complexity of calibrating the sensor, or eliminates the need for calibration at all.

Also, since the light source 3 includes a laser diode, an additional selective method of stabilizing the wavelength of light emitted by the light source 3 can be used (in addition to the method described in the first embodiment). This method is realized by additionally arranging the wavelength stabilizing element 24 in the path of the light 21 emitted from the laser diode 4. In this example, the wavelength stabilizing element 24 is a surface diffraction grating, but the wavelength stabilizing element 24 is more preferably a holographic diffraction grating having an aluminum layer on the surface and having 3,600 lines / mm lines. . However, similar performance can be obtained using other diffraction gratings. For example, (1) a holographic diffraction grating having more or less lines than 3,600 lines / mm , (2) a holographic diffraction grating having a surface of a silver layer or a layer made of another material, and (3) engraving diffraction. Or (4) a volume holographic diffraction grating. Further, the same performance can be obtained by using a band-pass filter combined with a dichroic mirror or another mirror that reflects light in a narrow wavelength band toward the direction of the solid-state light emitting element. A lens is disposed between the solid state light emitting device 4 and the surface diffraction grating. The lens condenses the light emitted from the solid state light emitting device 4 almost in parallel. The parallel light propagates in the direction of the surface diffraction grating. The surface diffraction grating is oriented so that the light 21 from the solid-state light-emitting element 4 propagates in the direction of the solid-state light-emitting element 4 through first-order diffraction (or higher-order diffraction) (that is, in the same light path). Opposite direction). This is a configuration of a Littrow type external resonant diode laser. Due to the diffracted light, the solid state light emitting device 4 selectively emits light having a wavelength similar to the wavelength of the light propagated from the surface diffraction grating toward the solid state light emitting device 4. Depends on the orientation of the. For example, when the grating has a line of 3,600 lines / mm , the incident angle of the light 21 with respect to the surface diffraction grating is about 23.3 ° for a wavelength of about 220 nm and about 23.9 for a wavelength of about 225 nm. °. Therefore, the wavelength of the emitted light is stable with respect to the fluctuation of the wavelength generated regardless of the action of the surface diffraction grating. The zero-order diffracted light from the surface diffraction grating (that is, regular reflection from the surface diffraction) is coupled toward the specimen and used to measure the absorbance of the object. The ratio of the light intensity of light incident on the surface diffraction grating from the solid light emitting element 4 and returning from the surface diffraction grating in the direction of the solid light emitting element 4 is in the range of 5% to 95%. A range is more preferable. When the ratio of returning to the direction of the solid state light emitting device 4 is high, the wavelength is further stabilized. The method for stabilizing the wavelength in this way may be combined with means such as the auxiliary temperature control element 25 described in the first embodiment.

By using a laser diode as the solid state light emitting element 4, there is an additional advantage that laser light as a high-quality light beam can be easily formed into parallel light. In this way, the incident light 6 incident on the specimen can be confined in a small cross-sectional area (area based on a plane perpendicular to the light propagation direction). This has a very important effect for a low-cost sensor. The first window 10 and the second window 11 may have a small cross-sectional area. Materials suitable for windows having a high transmittance for light of wavelengths from 200 nm to 220 nm are relatively costly, so the ability to use small windows is an important advantage. Furthermore, the means for cleaning the first window 10 and the second window 11 during operation of the sensor device is low cost and becomes more compact if the window is small. Therefore, the cost and size of the entire sensor device can be suppressed. In this example, the first window 10 and the second window 11 are about 2 mm × 2 mm in size. The high quality of the light emitted by the laser diode has the further effect that the laser light is collected by the lens and the collected light can be collected in a small spot. Therefore, the first light detection means (optionally the second light detection means) can be a small and low-cost device. In this example, the first light detection means is a silicon-based photodiode having a cross-sectional area of less than 1 mm ² .

  By using a laser diode as the solid-state light emitting element 4, a further effect that the light emitted from the laser diode is highly linearly polarized is brought about. Accordingly, in this example, the incident light 6 is p-polarized light, the incident light 6 is incident on the first window 10 at a Brewster angle, and the first window 10 and the second window 11 are parallel to each other. The first window 10 and the second window 11 are configured. When light is incident at the Brewster angle, reflection loss can be suppressed, and thereby the light intensity of the light incident on the first light detection means 9 can be increased. In the first window 10 and the second window 11 made of UV fused silica, the incident angle of light in the air is about 56 °.

Third Embodiment Next, a third embodiment of the present invention will be described. The third embodiment is similar to the first embodiment and the second embodiment, and the description of the configuration common to the first embodiment and the second embodiment will not be repeated. In the third embodiment shown in FIG. 5, far ultraviolet rays in the wavelength region of 200 nm to 240 nm are generated by frequency-converting longer wavelength light emitted by the solid state light emitting device. The solid-state light emitting device is a semiconductor laser, and a laser diode is an example.

The sensor device includes a light source 30. In the light source 30, the solid-state light emitting element 4 is a semiconductor laser that emits light 21 that passes through one or more frequency conversion elements 31. The semiconductor laser emits light having a center wavelength of about 400 nm or more and about 480 nm or less. In this embodiment, the semiconductor laser emits light 21 having a center wavelength of about 450 nm. In this embodiment, the semiconductor laser includes a Fabry having an Al _y In _x Ga _1-xy N semiconductor material and an Al _y In _x Ga _1-xy N light emitting layer (0 ≦ x ≦ 1 and 0 ≦ y ≦ 1).・ Perot laser diode. However, other types of semiconductor lasers can be used. Such other types of semiconductor lasers include vertical cavity surface emitting laser diodes, DBR laser diodes, DFB laser diodes, and lasers with other materials. The light emitted by the laser diode is condensed into substantially parallel light by the lens and enters the wavelength stabilizing element. An example of a suitable lens is a molded glass aspheric lens having a focal length of 2 mm to 5 mm. In this embodiment, the wavelength stabilizing element 24 is a surface diffraction grating, but is more preferably a holographic diffraction grating having an aluminum layer on the surface and 3,600 lines / mm line. However, similar performance can be obtained using other diffraction gratings. For example, (1) greater than 3,600 present / mm, or holographic diffraction gratings having a smaller line than 3,600 present / mm, the holographic grating having a surface layer of (2) Silver layers or other materials, (3) a scored diffraction grating or (4) a volume holographic diffraction grating. Further, similar performance can be obtained by using a band-pass filter combined with a dichroic mirror or another mirror that reflects light in a narrow wavelength band toward the laser diode. The surface diffraction grating is oriented so that the laser diode light 21 (light after being collected by the lens) propagates in the direction of the laser diode via first order diffraction (or higher order diffraction) (ie, , Opposite direction of the same light path). This is a configuration of a Littrow type external resonant diode laser. Due to the diffracted light, the laser diode selectively emits light having a wavelength similar to that of the light propagating from the surface diffraction grating in the direction of the laser diode. Depends on direction. For example, when the grating has a line of 3,600 lines / mm , the incident angle of the light 21 to the surface diffraction grating is about 50.7 ° for a wavelength of about 430 nm and about 52.4 for a wavelength of about 440 nm. Is about 54.1 ° for a wavelength of about 450 nm and about 55.9 ° for a wavelength of about 460 nm. Therefore, the wavelength of the emitted light is stable with respect to the fluctuation of the wavelength generated regardless of the action of the surface diffraction grating. The zero-order diffracted light from the surface diffraction grating (that is, regular reflection from the surface diffraction) can be coupled toward the frequency conversion element 31 using one or more lenses. A suitable lens is a spherical lens with a focal length of 5 mm to 200 mm, preferably 30 mm to 150 mm. Alternatively, a suitable system comprises two cylindrical lenses. Each of the two cylindrical lenses has a focal length of 5 mm to 200 mm (the focal lengths of the two lenses may be different from each other). Here, the first cylindrical lens condenses on the first plane, and the second cylindrical lens condenses on the second plane which is a plane perpendicular to the first plane. The ratio of the light intensity of light incident on the surface diffraction grating from the laser diode and returning from the surface diffraction grating in the direction of the laser diode is 5% to 95%, more preferably 5% to 20%. When the ratio of returning to the direction of the solid state light emitting device 4 is high, the wavelength is further stabilized. Laser diodes emit light through their surface, which may be anti-reflective coated so that the reflectivity is less than 2%. Thereby, the wavelength can be further stabilized. However, the surface of the laser diode does not necessarily need to be provided with a non-reflective coating, and in this example, the surface of the laser diode is not provided with a non-reflective coating.

The frequency conversion element 31 includes a β-BaB ₂ O ₄ crystal that provides a type 1 phase matching condition for second harmonic generation (SHG) of light emitted from the laser diode. The β-BaB ₂ O ₄ crystal has a length (measured in a direction parallel to the propagation direction of light passing through the crystal) of 1 mm to 20 mm, more preferably 5 mm to 15 mm. (1) The preferred direction of pump light in BaB ₂ O ₄ that leads to type 1 phase matching conditions for second harmonic generation (SHG) and (2) the preferred polarization direction of pump light are both prior art. For example, the wavelength of light emitted from the laser diode is about 450 nm, and light having a wavelength of about 450 nm propagates at an angle (θBBO) of about 63 ° away from the optical axis of the β-BaB ₂ O ₄ crystal. The main electric field of light is perpendicular to the optical axis. The frequency conversion element 31 converts a part of light having a center wavelength of about 450 nm into light having a center wavelength of about 225 nm. Light having a central wavelength of about 225 nm preferably has a light intensity of at least 1 μW, and more preferably has a light intensity of at least 10 μW.

  Light 32 having a first center wavelength 450 nm and a second center wavelength 225 nm is emitted from the frequency conversion element 31. The light is collected almost parallel by the lens. The light 32 is filtered by the filter 33. The filter 33 reduces the light intensity of the light having the first center wavelength to be lower than the light intensity of the light having the second center wavelength. It is preferred that most of the light 5 emitted from the filter has a second center wavelength. Most preferably, at least 90% of the light intensity of the light 5 is light having the second central wavelength. Frequency conversion (eg, SHG) may be relatively inefficient. Therefore, the light intensity of the light having the first center wavelength in the light 5 may be less than 0.01%, and the light intensity of the light having the first center wavelength in the light 32 may be less than 0.001% or less than 0.0001%. The filter may comprise one or more mirrors having a distributed bragg reflector (DBR). The DBR has a high reflectance with respect to the light having the second central wavelength (R> 90%, preferably R> 99%), and has a low reflectance with respect to the light having the first central wavelength. (R <1%). Suitable DBR mirrors are made using MgF2 and LaF3 layers on a UV fused silica substrate. The filter also includes a dispersible member. The dispersive member is, for example, a UV fused silica prism (that is, a Pellin-Broca prism or an equilateral prism). The dispersive member is provided so that light of λ = 450 nm and light of λ = 225 nm are spatially separated.

  As in the first embodiment, the incident light 6 enters the specimen, and the transmittance of the light passing through the specimen is measured by the first light detection means 9. Furthermore, the light intensity of the incident light 6 incident on the specimen is determined using the second light detection means 20 that detects a part of the light 5 emitted by the light source 3. The second light detection means 20 may be used to determine the fluctuation of the light intensity of the light 5, but this determination may be performed by another method described in the above embodiment. In this way, nitrate ions are determined according to the detailed description and the method described in the first embodiment.

  Similar to the second embodiment, the first window 10 and the second window 11 are preferably as small as about 2 mm × 2 mm. This is the size measured in the direction perpendicular to the propagation direction of the light 6. Thereby, the high quality which the light of the 2nd wavelength produced | generated with the frequency conversion element has can be enjoyed as an advantage. However, the first window 10 and the second window 11 having a smaller size or a larger size (for example, 5 mm × 5 mm, 10 mm × 10 mm, or a larger size) may be used. Similar to the second embodiment, the first window 10 and the second window 11 may be arranged in the direction of the Brewster angle with respect to the p-polarized light of the second wavelength. Thereby, the advantage that the light of the said 2nd wavelength produced | generated with the frequency conversion element is substantially linearly polarized can be enjoyed. Furthermore, since the light source 30 includes the frequency conversion element 31, (1) the degree of linear polarization of the frequency-converted light is extremely high, and (2) the degree of linear polarization of the frequency-converted light is generally There are further advantages, such as higher than the degree of linear polarization of light emitted by a typical fixed light source (eg, laser diode). The first light detection means and the second light detection means include a silicon-based photodiode (eg, a UV enhanced silicon photodiode).

  The light source 30 provided in the sensor device in the above-described embodiment includes the wavelength stabilizing element 24 disposed between the laser diode and the frequency conversion element 31. As a configuration that can be adopted in addition to the light source 30, the frequency conversion element 31 and the filter 33 are respectively disposed between the laser diode and the wavelength stabilizing element 24. A possible other configuration of the light source 30 is shown in FIG. The light 21 emitted by the laser diode 4 has a first center wavelength and enters the frequency conversion element 31. The light 34 propagated from the frequency conversion element 31 includes the light having the first center wavelength and the frequency conversion light having the second center wavelength. The light 34 is separated into light 35 and light 5 by the filter 33. The light 35 includes at least 10%, preferably 80% of the light having the first central wavelength. The light 5 includes light having the second center wavelength. The light 35 enters the wavelength stabilizing element 24. The wavelength stabilizing element 24 returns a part of the light 35 in the direction of the laser diode. A part of the light 35 travels in the same path as the path incident on the wavelength stabilizing element 24, but travels in the opposite direction and passes through the filter 33 and the frequency conversion element 31 (as described in the above example). It is preferable to dispose a lens that condenses the branched light into substantially parallel light or a lens that condenses the wavelength stabilizing element 24 between the frequency conversion element 31 and the wavelength stabilizing element 24. The light 5 is used in the sensor device as described in the first embodiment or the second embodiment. The parts group included in the light source shown in FIG. 18 is the same type as that described in the present example for the light source shown in FIG. 2, but the surface diffraction grating used as a wavelength stabilizing element is the surface diffraction. The difference is that at least 60% (more preferably at least 80%) of the light incident on the grating is returned in the direction of the laser diode.

  Throughout this embodiment, it is emphasized that the wavelength stabilizing element 24 acts on the light directly emitted from the laser diode and does not act on the frequency-converted light.

  In order to further stabilize the wavelength of the frequency converted light having the second wavelength contained in the incident light 5, a temperature control element may be applied to the frequency converting element 31. This configuration is effective. This is because if the frequency conversion element is maintained in a narrow temperature range (for example, ± 5 ° C.), the wavelength of the second central wavelength light obtained by frequency conversion in the frequency conversion element can be further stabilized.

  In addition to this, or as an alternative to the wavelength stabilization using the wavelength stabilizing element 24 described in the present embodiment, other means described in the first embodiment (such as the auxiliary temperature control element 25) are also third. It may be included in the embodiment.

  When the temperature control element 25 is used as in the method 2 of the first embodiment, the temperature control element acts on the solid state light emitting element 4 (in this embodiment, a laser diode). One or more frequency conversion elements 31 may be in thermal contact with the laser diode. One or more filters 33 may be in thermal contact with the laser diode.

  Alternatively, all frequency stabilizing means may be omitted. In this case, the effect of frequency conversion can be obtained. That is, it is possible to obtain an effect of suppressing the influence of the wavelength variation due to the solid light emitting element on the wavelength variation of the light incident on the specimen. Alternatively, it may be advantageous to use the temperature sensing means 27 and known changes with the temperature of the first center wavelength and / or the second center wavelength.

  As in the first and second embodiments, the first light detection means 9 and, in some cases, a controller 23 that receives input from the second light detection means 20 may be included. The controller 23 may accept inputs from the first light detection means and the second light detection means 20 in order to measure the absorbance A. Furthermore, the controller 23 may use a certain algorithm to determine the concentration of the object 1. For example, the controller 23 may include a microcontroller / microprocessor and other electrical circuitry. Further, the controller 23 may include a current generating unit that supplies a current to any part of the light source 3 including the solid state light emitting device 4.

In the third embodiment, the frequency conversion element including β-BaB ₂ O ₄ has been described. The frequency conversion element includes any material capable of generating light of a desired second center wavelength. For example, the frequency conversion element includes one or more of the following materials. _{β-BaB 2 O 4, Ba} 1-x B 2-yz O 4 - Si x Al y Ga z (0 ≦ x ≦ 0.15,0 ≦ y ≦ 0.10,0 ≦ z ≦ 0.04, x + y + z ≠ 0), SiO ₂ (for example, including a periodic twin structure that provides quasi-phase matching conversion), Al _y Ga _1-y N (0.5 ≦ y ≦ 1) (for example, periodic polarization that provides quasi-phase matching conversion) Inversion structure), CsLiB ₆ O ₁₀ , LiB ₃ O ₅ , KBe ₂ BO ₃ F ₂ , Li ₂ B ₄ O ₇ , LiRbB ₄ O ₇ , or MgBaF ₄ (eg, a periodically poled structure that results in quasi-phase conversion).

Fourth Embodiment Next, a fourth embodiment of the present invention will be described. The fourth embodiment is similar to the third embodiment, and the description of the configuration common to the third embodiment will not be repeated. In the fourth embodiment shown in FIG. 9, the sensor device includes any one of the sensor devices described in the first embodiment to the third embodiment (here, the first embodiment to the first embodiment). Any one of the sensor devices described in the third embodiment is referred to as a “first sensor”). One or more auxiliary sensors are referred to as “second sensors”. The measurement value of the second sensor is used to increase the accuracy with which the first sensor determines the object concentration in the sample. The second sensor may include any configuration described in the first to third embodiments. In addition, however, the light source 40 of the second sensor emits light having a wavelength greater than about 240 nm.

In the fourth embodiment, the first sensor is the same as the sensor device described in the third embodiment. For example, the light source 30 is the same as that in the third embodiment. In the fourth embodiment, one second sensor is used, which is described in FIG. This second sensor measures the transmittance of light having a central wavelength of about 375 nm that passes through the specimen. The second sensor is used to determine the characteristics of the sensor device (for example, cleanliness of the first window 10 and the second window 11), or the characteristics of the sample (for example, turbidity of the sample, or in the sample) Concentrations of chemicals other than the target substance). One or more of these known or estimated characteristics of the light transmission measured by the first sensor are subsequently used to increase the accuracy with which the sensor device determines the object concentration. Specifically, the second sensor is used to determine a suitable loss _Ti value for the first sensor. As a result, the second sensor considers the T _i value when calculating the concentration of the object in the sample using the output from the first sensor. In this configuration, when the _Ti value changes during use of the sensor, for example, when the first window 10 and the second window 11 become dirty with the passage of time, the turbidity of the specimen greatly changes with the passage of time. Are particularly advantageous.

  In the fourth embodiment, the second sensor is used to measure the turbidity of the specimen. The first sensor and the second sensor are arranged to act on the same specimen 2. The first sensor and the second sensor may share one sample processing means 12. The first sensor and the second sensor may use the same first window 10. The first sensor and the second sensor may use the same second window 11.

The light source 40 includes a solid light emitting element 41. The solid state light emitting device 41 emits light having a central wavelength of about 375 nm. In this embodiment, the solid state light emitting device is an LED. For example, the LED includes an Al _y In _x Ga _1-x N material (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). The light source 40 further includes a temperature control unit 42 and / or a temperature detection unit 43. The second sensor includes third light detection means 46 and auxiliary fourth light detection means 47 in order to measure the transmittance of light emitted from the light source 40 in the specimen (see FIG. 9). Then, the measured value P ₄ and the additional P ₅ to P ₄ / P ₃ ratio are measured, where the third light detection means 46 and the fourth light detection means 47 are the first light included in the first sensor. It operates in the same manner as the detection means 9 and the second light detection means 20). The third light detection means 46 and the fourth light detection means 47 are photodiodes that take into consideration the same design as the photodiodes in the first embodiment (for example, silicon-based photodiodes).

The concentration of the object 1 (nitrate ions in this embodiment) in the specimen 2 (water in this embodiment) is, for example, the first light detection means 9, the third light detection means 46, and additionally the second light. It is determined by the controller 23 using the inputs from the detection means 20 and the fourth light detection means 47. The calculation is executed by adding the following additional processing to the first embodiment. The light intensities of the light incident on the third light detection means 46 and the fourth light detection means 47 during the calculation process described in the first embodiment are P ₄ ′ and P ₅ ′, respectively. It is preferable that the sample used in the calculation process has negligible turbidity compared to the sample to be analyzed next by the sensor device. The specimen is preferably deionized water. While the sensor device analyzes the specimen, a transmittance T ³⁷⁵ nm of light having a central wavelength of about 375 nm passing through the specimen is calculated based on the measured light intensity P ₄ and auxiliary intensity P ₅ .

When the auxiliary fourth light detection means 47 does not exist, the value of P ₅ ′ / P ₅ may be estimated (for example, P ₅ ′ / P ₅ = 1). T ^{375 nm} is used to determine the effect of turbidity on the transmittance of light passing through the specimen in the first sensor. For example, when the center wavelength of the incident light 6 in the first sensor is about 225 nm, the light loss T ^{225 nm} in the analyze caused by the turbidity with respect to the light of wavelength 225 ^nm is determined as T ^{225 nm} = g (T ^{225 nm} ). Is done. Here, the mathematical function g () is determined theoretically, empirically, or semi-empirically. Subsequently, T ^{225 nm} is used as one of a plurality of denominators T _{i in} the equation for the light intensity of part of the light transmitted by the first sensor. This equation includes light loss that is not due to light absorption by the object and has been previously described in the detailed description. For example, the concentration of the object is calculated using the following equation:

Thereby, as explained in the detailed description, when the measurement is actually performed instead of the estimation of the value, the loss of a part of the light in the first sensor due to one or more causes that is not the absorption by the object is caused. The advantage of being quantified is enjoyed.

  Multiple sensors do not need to measure data simultaneously. When sensors are placed in a straight line for continuous monitoring and the measurement position of one sensor is in the wake of the measurement position of another sensor, it is convenient to have a time delay between measurements. By grasping the flow rate of the sample, the measurement timing is measured so that the same amount of sample exists in the measurement paths of both sensors. This makes the system resistant to rapid changes in conditions. The flow rate of the specimen is measured using a flow sensor, and the information is input to the controller 23. This allows for various time delays between measurements based on known flow rates.

In this embodiment, light having a wavelength of about 375 nm is used in the second sensor. However, other wavelengths of light may be used. The wavelength of the light used by the second sensor is preferably a wavelength that is not significantly absorbed by the object. Other wavelengths that provide similar corrections to obtain other effects may be used. For example, an LED that emits light having a wavelength of about 250 nm reduces light loss at the first sensor (T _i ) due to organic substances present in the system (for example, the specimen 2, the first window 10, and the second window 11). It may be used to measure. A plurality of second sensors may be used to obtain an estimate of one or more T _i for the first sensor. Thereby, the accuracy of the first sensor can be increased.

Fifth Embodiment Next, a fifth embodiment of the present invention will be described. The fifth embodiment is similar to the fourth embodiment. Common configurations are given the same reference numerals and their description will not be repeated. For example, the light source 30 and the light source 40 are the same as the light sources used in the fourth embodiment. A fifth embodiment is described in FIG. In the fifth embodiment, the first light detection means 9 has a light intensity (P ₂ ) of light emitted from the light source 30 and transmitted through the specimen, and a light intensity (P ₂ ) of light emitted from the light source 40 and transmitted through the specimen ( Used to measure P ₄ ). The auxiliary second light detection means 20 measures the light intensity (P _R ) of the light emitted by the light source 30 and the light intensity (P ₅ ) of the light source 40. The auxiliary mirror 28 is configured to direct the light emitted from the light source 30 and the light source 40 toward the first light detection means 9 and the second light detection means 20.

One possible configuration is described in FIG. In this configuration, the mirror 28 reflects light emitted from the light source 40 with a reflectivity of 1% to 99%, preferably 40% to 90%. The reflected light is incident light 49 having a light intensity P3. Incident light 49 enters the specimen and then enters the first light detection means 9. Of the light emitted from the light source 40, all or part of the light not reflected by the mirror 28 passes through the mirror 28 and enters the second light detection means 20. The light intensity of the transmitted light is P _5. Thus, the first light detection means 9 and the second light detection means 20 function in the same manner as the third light detection means 46 and the fourth light detection means 47 in the fourth embodiment, respectively. The mirror 28 reflects the light emitted from the light source 30 with a reflectance of 1% to 99%, preferably 10% to 60%. The reflected light is incident on the second light detection means 20. The light intensity of the transmitted light is PR. Of the light emitted from the light source 30, all or part of the light not reflected by the mirror 28 passes through the mirror 28. The transmitted light is incident light 6 having a light intensity P ₁ . Incident light 6 enters the specimen and then enters the first light detection means 9.

  The incident light 6 and the incident light 49 preferably propagate through similar optical paths in the specimen, for example, similar positions of the first window 10 and the second window 11. Thus, the first sensor system and the second sensor system according to the fourth embodiment are incorporated into the fifth embodiment with a small number of parts (that is, the third light detection means and the fourth light detection means are not required). ).

In the fifth embodiment, the light source 30 and the light source 40 preferably do not emit light simultaneously. One possible driving method is described in FIG. This will be described below. By energizing the light source 30 at time t _1, power source 30 is turned ON. Thereby, the light source 30 emits light. Thereafter, at time t ₂ (t ₂ > t ₁ ), power supply to the light source 30 is completed, and the power source of the light source 30 returns to the OFF state. The measured value (P ₂ ) of the first light detection means 9 is acquired between t ₁ and t ₂ . The measurement value (P _R ) of the second light detection means 20 may be acquired between t ₁ and t ₂ . Also, by energizing the light source 40 at time t _3, the power of the light source 40 is turned ON. Thereby, the light source 40 emits light. Thereafter, at time t ₄ (t ₄ > t ₃ ), power supply to the light source 40 is completed, and the power source of the light source 40 returns to the OFF state. The measured value (P ₄ ) of the first light detection means 9 is acquired between t ₃ and t ₄ . The measurement value (P ₅ ) of the second light detection means 20 may be acquired between t ₃ and t ₄ . The controller 23 may be used for operating the light source 30 and the light source 40 and receiving inputs from the first light detection means 9 and the second light detection means 20. As described in FIG. 10, continuous measurement may begin at time t ₅ .

As in the fourth embodiment, the measured values (P ₂ , P _R ) and (P ₄ , P ₅ ) acquired between t ₁ and t ₂ and between t ₃ and t ₄ are the subjects in the sample. Used to calculate the concentration of ions.

As the light source 30 and the light source 40 is not operated at the same time, t ₁ and preferably (t3> t2 and t5> t4) that while do not overlap each other t between ₂ and t ₃ and t _4. t1, t2, t3, and t4 are preferably extremely wide values. For example, both (t2-t1) and (t4-t3) are in the range of 1 μs to 1 s, more preferably 0.1 ms to 50 ms. (T3-t2) is preferably less than 1 s. In the fifth embodiment, (t2-t1) and (t4-t3) are about 20 ms, and (t3-t2) is about 2 s.

  In particular, when the incident light 6 and the incident light 49 propagate through similar optical paths in the specimen, the fifth embodiment has a plurality of advantages. First, the first window 10 and the second window 11 of the sample processing means 12 are minimized, which leads to cost reduction. Second, when at least one of the first window 10 and the second window 11 has a high absorbance due to contamination due to growth of living things, the first light (that is, light from the light source 30). And the second light (that is, the light from the light source 40) contacts the same degree of dirt. This is because the purpose of measuring the transmittance of light radiated from the light source 40 and propagating through the first window 10, the second window 11, and the specimen 2 is radiated from the light source 30 and the first window 10, second window 11. This is particularly advantageous when measuring the influence of dirt on the first window 10 and the second window 11 on the transmittance of light propagating through the specimen 2.

Third, when the time between measurements (t3-t2) is small, the location of the specimen measured by each sensor is almost the same. Thus, due to the heterogeneity of the sample, any error in the correction factor T _i is minimized, is done with high accuracy in calculating the ion concentration of interest.

  The sensor device according to the fifth embodiment is for measuring nitrate ion concentrations in a plurality of different water sample specimens having a low nitrate ion concentration (less than 100 mg / litre) and a high nitrate ion concentration (greater than 100 mg / litre). Used for. For each specimen, the nitrate ion measured by the sensor device described in FIG. 11 was compared with the measured value obtained by cadmium colorimetric analysis, which was well established as a method for measuring nitrate ion concentration.

  The sensor device used for the specimen having a low nitrate ion concentration is configured such that the light from the light source 30 and the light from the light source 40 propagate through the specimen at a distance L = 10 mm. Samples with low nitrate ion concentrations include three “references” (deionized water with known potassium nitrate concentration), five “tap waters” (potable tap water from several European locations), and the UK Including “groundwater” collected from a well with a pit. The colorimetric quantitative analysis and the nitrate ion concentration measured by the apparatus containing the present invention are described in FIG. The colorimetric quantitative analysis and the measurement results of the respective samples obtained using the sensor device of the present example are plotted as adjacent bar graphs without being separated from each other.

  The sensor device used for the specimen having a low nitrate ion concentration is configured such that the light from the light source 30 and the light from the light source 40 propagate through the specimen at a distance L = 1 mm. The plurality of specimens having a high nitrate ion concentration include “fish farm water” and “hydroponics water”. The fish farm water was collected from a fish tank in a seawater fish farm on the surface. Hydroponics water was collected from the water supplied to the hydroponics plant. The nitrate ion concentration measured by the colorimetric quantitative analysis and the apparatus including the present invention is shown in FIG.

  For all the specimens, a very high agreement was found between the nitrate ion concentration measured by the sensor device according to the present invention and the nitrate ion concentration obtained by cadmium colorimetric analysis (FIGS. 12 and 13). The excellent correlation between the cadmium colorimetric quantitative analysis and the fifth example demonstrates the effectiveness of the present invention.

  Another sensor device according to the fifth embodiment was used to measure the nitrate ion concentration in water ranging from 0 mg / litre (deionized water) to 1,550 mg / litre. These specimens were prepared by diluting standard nitric acid solutions provided by the National Institute of Standards and Technology (NIST) with deionized water using various volumes of pipettes. . The sensor device is configured such that the light from the light source 30 and the light from the light source 40 propagate through the specimen at a distance L = 0.75 mm. The center wavelength of light emitted from the light source 30 is 223 nm. The measurement results are indicated by dots in FIG. In FIG. 22, a broken line shows ideal sensor performance.

  In addition, two specimens collected from two points in a hydroponics company were measured. One specimen is water before being supplied to the growing plant. The other specimen is the return water after being supplied to the growing plant. This hydroponics company is different from the company that produced the measurement results of FIG. The measurement results are shown as point data in FIG. The actual nitrate ion concentration was measured by UV mass spectrometry using a Perkin-Elmer Lambda950 spectrophotometer adjusted with NIST standard nitric acid.

  For all the specimens described in the above two paragraphs, nitrate ion concentration measured by the sensor device according to the present invention and known diluted NIST standard nitric acid (FIG. 22) or adjusted UV mass spectrometry in a standard laboratory facility ( A very high agreement was found with the nitrate ion concentration obtained by FIG. The excellent correlation between these methods and the sensor device according to the fifth embodiment further proves the effectiveness of the present invention.

  This sensor device can measure a higher nitrate ion concentration than a known sensor device while maintaining extremely high linearity. This improved performance can be seen from FIG. The light source used in the sensor device according to the present invention has a narrow spectral bandwidth of FWHM≈0.1 nm. In contrast, a known sensor device has a FWHM of 0.5 nm or more. FIG. 24 shows the absorbance dependence on nitrate ion concentration for multiple light sources having a central emission wavelength of λ = 223 nm, a path distance L = 0.75 mm in the specimen, but different spectral bandwidths. As can be seen from FIG. 24, the non-linearity increases as the spectral bandwidth increases, and deviates from the ideal sensor performance as the nitrate ion concentration increases. High linear performance allows a simplified calibration process to be used, and nitrate ion concentrations can be accurately measured over a wide concentration range.

Sixth Embodiment Next, a sixth embodiment of the present invention will be described. A sixth embodiment is described in FIG. The sixth embodiment has the same configuration as the third embodiment, the fourth embodiment, and the fifth embodiment. Common configurations are given the same reference numerals and their description will not be repeated. The sensor device according to the sixth embodiment includes a light source 30 including a frequency conversion element 31. In the light source 30, the light emitted from the light source 30 has a first center wavelength (that is, a part of the light emitted by the solid state light emitting device 4, described as light 36 in FIG. 19) and a second center wavelength (that is, frequency conversion). (Denoted as light 5 in FIG. 19). In this sixth embodiment, the light 36 is used in the same manner as the light emitted by the light source 40 of the fourth embodiment. Referring to FIG. 19 as an analogy with the fourth embodiment, the light 5 is a first sensor (first light detection means 9, auxiliary second light detection means 20, and auxiliary mirror 22). The light 36 is used by the second sensor (using the third light detecting means 46, the auxiliary fourth light detecting means 47, and the auxiliary mirror 37). The sixth embodiment is more advantageous than the fourth embodiment in that the light source 40 is not required.

  The light source 30 of the sixth embodiment is identical to the light source described in the fourth embodiment, except that a filter 33 is provided for both light 36 and light 5. The filter 33 is configured such that the light intensity of the light 36 is greater than the value obtained by adding 0.01 to the light intensity of the light 5 and less than the value obtained by adding 10 to the light intensity of the light 5. Is preferred. The filter 33 may include one or more mirrors described in the third embodiment.

  In FIG. 19, light 36 and light 5 are indicated by separate lines. However, light 36 and light 5 may travel in substantially the same path. The auxiliary mirror 22 makes the light of the second center wavelength stronger than the light of the first center wavelength so that the light intensity of the light of the second center wavelength is measured from the light incident on the second light detection means. It is configured to reflect. The auxiliary mirror 37 makes the light of the first center wavelength stronger than the light of the second center wavelength so that the light intensity of the light of the first center wavelength is measured from the light incident on the fourth light detection means. It is configured to reflect.

Seventh Embodiment Next, a seventh embodiment of the present invention will be described. A seventh embodiment is described in FIG. The sensor device according to the seventh embodiment is similar to the sensor device according to the sixth embodiment. In the sixth embodiment, a part of the light having the first central wavelength emitted by the solid state light emitting device 4 is used to increase the accuracy of the concentration of the object measured by the first sensor. Used as light to. The light source 30 may be the same as the light source in the sixth embodiment. The light source 30 is operated under two or more different operating conditions. The light emitted by the light source 30 includes light 36 (light intensity P _a ) having a first center wavelength and light 5 (light intensity P _b ) having a second center wavelength. The ratio P _a / P _b is different for each of the two or more different operating conditions of the light source 30. For example, the two or more different operating conditions include “two or more different currents supplied to the solid state light emitting device 4”.

Different values of the ratios P _a / P _b are obtained by utilizing the nonlinear dependence of the light intensity of the frequency converted light generated by the frequency conversion element 31 with respect to the light intensity of the light 21 emitted from the solid state light emitting element 4. The The light intensity (P _a ) of the light 36 is proportional to the light intensity of the light 21. The light intensity (P _b ) of the light 5 is proportional to the light intensity of the frequency converted light generated by the frequency conversion element 31.

For example, the plot in Figure 21, schematically illustrating the dependence of P _a and P _b with respect to the current supplied to the solid-state light-emitting element 4 of the light source 30. As the current (I) increases, the light intensity (P _a ) of light having the first wavelength increases. According to this example, P _a is almost linearly dependent on the current (P _a ≈a ₁ + a ₂ I, a ₁ and a ₂ are constants). However, in this example, linear dependence is not essential. The light intensity of the light having the first wavelength at the first current (I = I ₁ ) is lower than the light intensity at the second current (I = I ₂ ; I ₂ > I ₁ ) (P _a (I ₁ ) < P _b (I ₂ )). Light intensity of the light having a second wavelength (P _b) is dependent on the non-linearly with the light intensity of the light (P _a) having a first wavelength _{(P b ≠ b 1 P a} ; wherein b ₁ is a constant) . In this particular example, dependence on P _a of P _b is a P _b ≒ b ₂ P _a ² (wherein b ₂ is a constant). This approximate dependency is typical of the light source 30 including frequency conversion by SHG. It may be used a non-linear dependence on P _a of P _b.

For nonlinear dependence on P _a of P _b, the ratio _{P a (I 1) / P} b (I 1) is different from the ratio _{P a (I 2) / P} b (I 2). For example, as shown in FIG. 21, P _a (I ₁ ) / P _b (I ₁ )> P _a (I ₂ ) / P _b (I ₂ ). The light source _{30, P a (I 1)>} h 1 P b (I 1), and P _b (I _2)> h is preferably _{2 P a (I 2) (} h 1 ≧ 1, h 2 ≧ 1,). More preferably, h ₁ ≈2 and / or h ₂ ≈2. More preferably, h ₁ > 2 and / or h ₂ > 2.

Light 5 and light 36 propagate through the same optical path in the direction of the specimen and pass through the specimen. For example, the light 5 and the light 36 pass through similar positions of the first window 10 and the second window 11. After passing through the specimen 2, the transmitted light 39 having the first center wavelength and the second center wavelength enters the first light detection means 9 (see FIG. 20). The light intensity of the light incident on the first light detection means is P ₇ , where P ₇ is the light intensity (P ₄ ) of the transmitted light having the first center wavelength and the light intensity of the transmitted light having the second center wavelength (P ₄ ). P ₂ ) (P ₇ = P ₂ + P ₄ ). The first light detection means 9 is used to determine P ₇ in at least two operating conditions of the light source 30. For example, there are two current values (P ₇ (I ₁ ) and P ₇ (I ₂ )).

The light intensity of the light incident on the specimen is P ₆ , and P ₆ is the total value of the light intensity (P ₃ ) of the light having the first center wavelength and the light intensity (P ₁ ) of the light having the second center wavelength. (P ₆ = P ₃ + P ₁ ). The values of P ₁ and P ₃ at two or more operating conditions of the light source 30 are determined for a particular light source. Thereafter, the measured value P ₇ for two or more operating conditions of the light source 30 is used to measure the transmittance at which the light having the first center wavelength and the light having the second center wavelength are transmitted through the system and the specimen, respectively. It is done. Thereby, a function similar to the “second sensor” and the “first sensor” in the previous embodiment is realized.

Second light detecting means 20 is used to determine the light intensity P _R. As described in the previous example, P _R is proportional to P _1. The light is coupled in the direction of the second light detection means 20 by the mirror 22. Preferably, the mirror 22 reflects part of the light having the second center wavelength, does not reflect much light having the first center wavelength, and does not reflect light having the first center wavelength and light having the second center wavelength. Partially penetrates. In this case, the light incident on the second light detection means 20 is substantially proportional to P ₁ . Alternatively, a filter (for example, a bandpass filter) may be used to suppress the total amount of light having the first center wavelength incident on the second light detection means 20.

Fourth optical detection means 47 is used to determine the light intensity P _5. As described in the previous examples, P ₅ is proportional to P ₃ . The light is coupled in the direction of the fourth light detection means 47 by the mirror 38. Preferably, the mirror 38 reflects a portion of the light having the first center wavelength, does not reflect much light having the second center wavelength, and does not reflect light having the first center wavelength and light having the second center wavelength. Partially penetrates. In this case, light incident on the fourth light detecting means 47 is substantially proportional to P _3. Alternatively, a filter (for example, a bandpass filter) may be used to suppress the total amount of light having the second center wavelength that is incident on the fourth light detection unit 47.

When the second light detection means 20 and / or the fourth light detection means 47 are used, in order to increase the accuracy of measuring the transmittance of light having the first center wavelength and the transmittance of light having the second center wavelength. , the measured value of P _R and / or P ₅ at two or more operating conditions of the light source 30 may be used together with the measurement values P ₇ in the two or more operating conditions.

The light system having the first central wavelength and the transmittance of the specimen influence the measurement using the first operating current (I ₁ ) (that is, a function similar to the “second sensor” in the previous embodiment). And so that the transmittance of the light system having the second central wavelength and the transmittance of the specimen influence the measurement using the second operating current (I ₂ ) (ie similar to the “first sensor” in the previous embodiment) Function), P _a (I ₁ ) >> P _b (I ₁ ) and P _b (I ₂ ) >> P _a (I ₂ ).

  By operating the light source 30 under two or more operating conditions (current in this embodiment), the transmittance of the light window having the first center wavelength and the specimen and the transmission of the light window having the second center wavelength and the specimen are transmitted. The rate is measured. Therefore, the advantage according to the sixth embodiment can be obtained with a small number of parts (that is, the third light detection means is not required).

Eighth Embodiment Next, an eighth embodiment of the present invention will be described. In the eighth embodiment shown in FIG. 14, auxiliary light detection means is added to measure the light intensity of the light scattered by the specimen. The auxiliary light detection means can be added to a sensor device configured according to any of the previous embodiments. The description of the configuration common to the previous embodiment will not be repeated.

  The sample processing means 12 is provided with an auxiliary window 50 so that light emitted from the light source 3 and scattered by the sample 2 at an angle θ with respect to the non-scattered light 8 is substantially transmitted from the sample processing means 12. It is done. The window 50 satisfies the same criteria as the first window 10 and the second window 11. The window 50 may be formed of the same material as the first window 10 and the second window 11. The scattered light 51 is associated with at least one light detection means 52. The light detection means 52 is designed in the same manner as the first light detection means 9. The light detection means 52 may include one or more photodiodes disposed at one or more positions, and thereby can detect light scattered by the specimen at one or more angles. For example, one scattering angle θ is described in FIG. The one or more angles are selected to be sufficiently large so that the transmitted light 8 does not affect the light detection means 52. The angle θ is 5 ° to 180 °, preferably 60 ° to 120 °. More preferably, the angle θ is about 90 °.

The output of the light detection means 52 is transmitted as an input to the controller by wireless means or wired means. The controller may be the same as the controller 23 that receives the signal from the first light detection means 9. The light intensity of light incident on the light detection means 52 is used to determine the characteristics of the system or specimen (eg, turbidity of the specimen) used to increase the accuracy of the concentration of the object measured by the sensor device. It's okay. Similar to that described in the fourth embodiment, this measurement result obtains one of a plurality of denominators T _i of an equation for the light intensity of a part of the light transmitted by the sensor device, and It may be used to increase the accuracy of the object concentration in the specimen measured by the sensor device.

  As described in the first embodiment, the light output from the light source 3 is output using the auxiliary second light detection means 20 in the same manner as the transmission light 8 incident on the first light detection means 9. You may correct | amend the fluctuation | variation of the light intensity of the light.

  An advantage of this apparatus is that only the light from the light source 3 is used to determine the characteristics (eg, turbidity) of the specimen, and the second light source 40 is not necessarily required.

  It is preferable to use a light source 3 including a solid-state light-emitting element 4 including a laser (when a light source 30 including a frequency conversion element 31 is used instead of the light source 30, the light source 30 is a solid-state light-emitting element that is a laser. 4). The use of a laser is advantageous because the laser has a high beam quality and / or the laser has a high degree of linear polarization. Scattered light from incident light having high beam characteristics (eg, collimated laser beam) is efficiently distinguished from incident light by the position of the light detection means 52. Light scattered from incident light having a high degree of linear polarization is efficiently distinguished from incident light because the scattered light has random linear polarization.

Ninth Embodiment Next, a ninth embodiment of the present invention will be described. The ninth embodiment relates to an improvement made to the specimen processing means 12 and is advantageous for the operation of the sensor device in some applications. The sensor system may be similar to any of the previous embodiments, and the description of the configuration common to the previous embodiments will not be repeated.

  During the operation of the sensor, the surfaces of the window 10 and the window 11 that come into contact with the specimen 2 may be covered with a substance that absorbs or scatters light emitted from any one of the light source 3, the light source 30, and the light source 40. This material includes bacteria, salt deposits, organic molecules, and other soils (dirt, mud, clay, etc.). If this additional light loss of the system (one of the multiple factor Tis described in the detailed description above) is not taken into account, the light absorption will contribute to the object 1 by mistake. Therefore, an error is included in the object concentration determined by the sensor. Therefore, it is desirable to keep the window 10 and the window 11 as uncontaminated as possible by the above substances. Or it is desirable to hold | maintain the window 10 and the window 11 in the state by which the influence by contamination does not change a lot. This is realized by the sample processing means 12 including a window cleaning means.

  The window cleaning means may be a wiper that physically contacts one or both surfaces of the window 10 and the window 11 that contact the specimen. The wiper may include, for example, nitrile rubber, silicon, or nylon. The wiper periodically wipes the surfaces of the window 10 and the window 11, including the entire surface of the window in which light from the light source 3 or the light source 30 propagates and contacts the specimen 2. The wiper may be driven by an electric motor. Alternatively, the motor may be driven by air or hydraulic pressure (water pressure).

  The window cleaning means may be a nozzle to which a compressible fluid is supplied. The fluid may be air. Alternatively, the fluid may be water. The nozzle includes the surface of one or both of the window 10 and the window 11, the surface of which the light 6 and light 8 propagate and the entire surface of the window in contact with the specimen 2 is included. Is angled so that flows.

  The window cleaning means may be one or more members designed to vibrate one or both of the window 10 and the window 11. For example, the member may be a lead zirconate titanate (PZT) based material that is driven at a frequency greater than 20 kHz to generate ultrasound. The one or more members may be directly attached to the window 10 and the window 11. Alternatively, the one or more members may be attached somewhere in the sensor that physically contacts the window 10 and the window 11.

  The user may arbitrarily set the time interval for operating the window cleaning means. For example, the window cleaning means may operate every minute, every 15 minutes, every hour, or every day. Alternatively, the window cleaning means may operate before the sensor device is used to obtain a measured value of the object concentration in the specimen. The window cleaning means may be operated by an auxiliary controller 23. The window cleaning means preferably does not operate while the sensor device is acquiring the measured transmittance value.

Tenth Embodiment Next, a tenth embodiment of the present invention will be described. A tenth embodiment is described in FIG. A warning is issued to monitor the concentration of ions, molecules, or atoms in the specimen and when the concentration exceeds the first set limit value and / or falls below the second set limit value Therefore, the tenth embodiment uses a sensor device configured according to any of the previous embodiments. This embodiment will be described with reference to a sensor device configured to measure the concentration of nitrate ions contained in water for human consumption.

  A sensor device 100 is disposed along the drinking water between a water source 60 and one or more use locations 61. The drinking water supply may be a municipal water purification plant. The drinking water can be a well of a groundwater source. For example, the sensor device may be installed on a water pipe where drinking water enters the house. Alternatively, the sensor device may be installed near the faucet (eg, under a kitchen sink). Or a sensor apparatus may be installed in a water purification plant.

  The result of the concentration measurement performed by the sensor device is compared with the first set limit value (for example, the upper limit value WHO 50 mg / litre of the nitrate ion concentration in the drinking water) by the controller 62. This comparison process is executed inside the sensor device by the same controller as the auxiliary controller 23. When the measured value exceeds the first set limit value, a signal for operating the alarm device 63 is transmitted. The alarm device 63 is installed in the vicinity of one or more use places 61, for example, and notifies the user that the water is not safe for drinking. The signal is transmitted by wireless means or wired means. The alarm may be an audio alarm, a visual alarm, or an audio / visual alarm.

Eleventh Embodiment Next, an eleventh embodiment of the present invention will be described. An eleventh embodiment is described in FIG. In order to monitor the concentration of ions, molecules or atoms in the specimen and to process the specimen when the concentration is outside the set range, the eleventh embodiment implements steps 1-9. One or more sensor devices 100 and sensor device 101 configured according to any of the examples are used. Alternatively, an auxiliary sensor device 65 of a type other than the disclosed invention may be used in combination with the one or more sensor devices 100 and the sensor device 101 described above.

  One or more sensor devices 100, sensor devices 101, and sensor devices 65 are installed between the sample source 60 and the sample use place 61. The first sensor device 100 measures the concentration of the object in the sample supplied from the sample source 60. If the object concentration in the sample determined by the first sensor device 100 is higher than the set limit value, the concentration adjustment is performed to reduce the object concentration in the sample before the sample is supplied to the use place 61. Means 64 is used. Alternatively, the second sensor device 101 may measure the object concentration in the sample supplied to the use place 61. The measurement results obtained by the sensor device 100, the sensor device 101, and the sensor device 65 are received by a controller 62 (for example, a microprocessor or a microcontroller) that controls the operation of the density adjusting unit 64. Appropriate use of the concentration adjustment means to supply the specimen to the point of use with the target concentration within the set range, and optimal use of the concentration adjustment means (for example, minimizing the power used by the concentration adjustment means) ) A first sensor device and a second sensor device are used.

  In the first usage method of the eleventh embodiment, the specimen is water, and the specimen source 60 is a well of a groundwater source. The place of use 61 is a faucet that supplies water with a nitric acid concentration equal to or lower than a set value (for example, the upper limit is WHO 50 mg / litre). The sensor device 100 and the sensor device 101 are sensor devices appropriately configured according to any of the first to ninth embodiments to measure nitrate ion concentration in water. The concentration adjusting means 64 (also referred to herein as a concentration fluctuation device) is a reverse osmotic pressure semen apparatus, an ion exchange semen apparatus, or other semen apparatus that can reduce the concentration of nitric acid in water. The nitric acid concentration in water determined by the sensor device 100 and the sensor device 101 is used to ensure that the nitric acid ion concentration in the water supplied to the place of use 61 is equal to or lower than the set value. The concentration measurement value is used to ensure that the concentration adjusting means is not used unnecessarily (for example, when the concentration of nitric acid in water supplied from the sample source 60 is already equal to or lower than the set value). This utilization method provides a drinking water source that minimizes energy and consumables for operating the concentration adjusting means (for example, reverse osmotic semen apparatus, ion exchange semen apparatus). Alternatively, for example, an alarm device 63 similar to the tenth embodiment that issues an alarm when the concentration of nitrate ions in the water supplied to the use place 61 is larger than the installation value due to a failure of the concentration adjusting means 64, for example. It may be included.

  In the second usage method of the eleventh embodiment, the specimen is water of a recirculating aquaculture system (RAS) in which the nitrate ion concentration in the recirculated water is maintained below a set value. The specimen source 60 is water supplied from a tank containing fish or other aquatic organisms (directly or via a storage tank). The place of use 61 is water returned (directly or via a storage tank) to a tank containing fish or other aquatic organisms. The sensor device 100 and the sensor device 101 are sensor devices configured according to any of the first to ninth embodiments in order to measure nitrate ion concentration in water. The concentration adjusting means 64 has an inlet for receiving water supplied from another water source. Another water source supplies water having a nitrate ion concentration lower than the set value. Thereby, when the water of another water source is added to the water of the specimen source 60, the concentration of nitrate ions in the water supplied to the place of use 61 can be reduced. The concentration of nitric acid in water determined by the sensor device 100 and the sensor device 101 is used to ensure that the concentration of nitrate ions in water supplied to the point of use is equal to or lower than the set value. The density measurement is used to ensure that the density adjustment means is not unnecessarily used. For example, if not required, the other source water is not added to the sample source water. With this method of use, for example, in order to grow fish in a productive manner, the nitrate ion concentration is below the set value, while minimizing the energy and water usage associated with adding water from another source. RAS system is brought. This method is particularly advantageous when water is low, or when the water must be heat treated and / or disinfected prior to adding water to the RAS system. The water may be sea water. Sensor device 100 and sensor device 101 may be combined with a sensor device 65 that monitors the concentration of other ions, other components, or other molecules in the water.

  In the third usage method of the eleventh embodiment, the specimen is water supplied to plants in an agricultural facility. For example, water is supplied to plants grown in hydroponics, aquaponics, or aerial cultivation. As this utilization method, plant cultivation by hydroponics is an example, and the nitrate ion concentration is maintained between a lower limit value and an upper limit value. The specimen source 60 is water supplied from the side of the plant to be cultivated (directly or via a storage tank). The place of use 61 is water returned to the plant to be cultivated (directly or via a storage tank). The sensor device 100 and the sensor device 101 are sensor devices configured according to any of the first to ninth embodiments in order to measure nitrate ion concentration in water. The concentration adjusting means 64 has one or more inlet portions from one or more tanks containing the stored nutrient solution. One or more stored nutrient solutions include a nitrate ion source. The nitrate ion source is, for example, ammonium nitrate or potassium nitrate. Therefore, by increasing or decreasing the proportion of the nutrient solution containing one or more nitrate ions added to the water, the nitrate ion concentration in the water at the place of use 61 is relative to the nitrate ion concentration in the water supplied from the sample source. Increase or decrease respectively. The concentration of nitric acid in water determined by the sensor device 100 and the sensor device 101 is used to ensure that the concentration of nitrate ions in the water supplied to the point of use is within a specific range. Concentration measurements are used to optimize the amount of stored nutrient solution added to the water. One or more auxiliary sensor devices 65 may be used. Such a sensor device 65 includes a PH sensor and / or an electrical conductivity sensor. The controller 62 uses these auxiliary sensors to further optimize the amount of other preserved nutrients added in response to changes caused by changing the amount of nutrient solution containing one or more nitrate ions. May be used. This method minimizes the use of stored nutrient solutions (reduces operating costs) and ensures a sufficient supply of nitrate ions to plants (optimizing yield and maximizing profits) However, hydroponic cultivation in which the nitrate ion concentration in water is maintained within a certain range is provided.

  The invention has been illustrated and described with respect to an embodiment or embodiments. However, after reading and understanding the present specification and the accompanying drawings, those skilled in the art will be able to make equivalent changes and improvements. In particular, for the various functions performed by the members (parts, assemblies, devices, components, etc.) described above, the language used to describe such members (including references to “means”) is: Unless otherwise indicated, any embodiment that performs a specific function of the above-described member, even if it does not have a structure equivalent to the disclosed structure that performs the above function in the illustrated embodiment or the embodiment according to the present invention. It is intended to correspond to a member (ie an equivalent function). Further, although specific structures according to the present invention may have been described for only one or several embodiments, such structures are required and advantageous for a given or specific application. May be combined with one or more structures according to other embodiments.

  The sensor device according to the present invention is used for measuring ion concentration (for example, nitrate ion in water). The sensor device may be used in certain devices to determine if water is not safe for human consumption. The sensor device may be used to optimize the wastewater treatment process. The sensor device may also be used in certain devices to determine if the water is harmful to fish in the farm due to the high nitrate ion concentration in the water and to improve yield. The sensor device may also be used in certain devices to determine if the nitrate ion concentration in water is at an optimal level for plant cultivation in hydroponic cultivation fields and to improve yield.

DESCRIPTION OF SYMBOLS 1 Object 2 Specimen 3 Light source 4 Solid light emitting element 5 Light 6 Incident light 8 Transmitted light 9 Light detection means 10 Window 11 Window 12 Specimen processing means 20 Light detection means 21 Light 22 Partial reflection mirror 23 Controller 24 Wavelength stabilization element 25 Temperature control Means 26 Wavelength filter 27 Temperature detection means 28 Mirror 30 Light source 31 Frequency conversion element 32 Light 33 Filter 34 Light 35 Light 36 Light 37 Mirror 38 Mirror 39 Transmitted light 40 Light source 41 Solid light emitting element 42 Temperature control means 43 Temperature detection means 46 Light detection Means 47 Light detection means 48 Partial reflection mirror 49 Incident light 50 Window 51 Light 52 Light detection means 60 Water source 61 Water use place 62 Controller 63 Alarm device 64 Concentration adjustment means 65 Auxiliary sensor device 100 Sensor device 101 according to the present invention Sensor device according to

Claims (19)

A sensor that measures the concentration of one or more types of ions, molecules, or atoms in a fluid,
A first photodetector for measuring the intensity of incident light;
A first light source including a solid state light emitting device,
The first light source emits light having a wavelength of less than 240 nm (nanometers) incident on the fluid, and the first photodetector detects light that has passed through the fluid,
The first light source further includes a frequency conversion element arranged to receive the light emitted from the solid state light emitting device,
The frequency conversion element converts the frequency of the light emitted from the solid state light emitting device to a wavelength of less than 240 nm (nanometers),
The light emitted from the solid state light emitting device has a wavelength in a range between a first wavelength and a second wavelength greater than the first wavelength;
The frequency conversion process of the frequency conversion element is one of second harmonic generation, third harmonic generation, fourth harmonic generation, fifth harmonic generation, sum frequency generation, and difference frequency generation. in the conversion process, the light having a first wavelength greater than the light and the second wavelength has a wavelength of less than wavelength sensor which is a light not light and phase matching frequency-converted. A controller that operates in connection with the first photodetector;
The controller determines the concentration of one or a plurality of types of ions, molecules, or atoms in the fluid based on a transmittance of light emitted from the first light source through the fluid. Item 2. The sensor according to Item 1. A second photodetector that is arranged to receive at least one of the light emitted from the first light source before passing through the fluid;
The controller operates while being connected to the second photodetector.
P ₂ is the intensity of light that passes through the fluid and is incident on the first light detection device, and is based on data output from the first light detection device,
When P ₁ is the intensity of light incident on the fluid and is based on the data output from the second photodetector,
The sensor of claim 2 in which light emitted from the first light source based on P ₂ / P ₁ is characterized in that to determine the transmission through the fluid.   The sensor according to claim 2, further comprising a sample processing unit including the fluid. The first photodetection device and the first light source constitute a first sensing element,
A second sensing element for determining at least one characteristic of the sample processing unit and the fluid;
5. The sensor of claim 4, wherein the controller uses the characteristics of the fluid and / or the sample processing unit to determine the concentration of ions, molecules, or atoms in the fluid.   The second sensing element has at least one of the turbidity of the fluid, the cleanliness of the sample processing unit, the concentration of organic molecules, and the concentration of one or more types of ions, molecules, or atoms in the fluid. The sensor according to claim 5, wherein the sensor is determined. Further comprising at least one auxiliary photodetector for measuring the intensity of the incident light;
The sensor according to claim 1, wherein the at least one auxiliary light detection device is arranged to receive light scattered by the fluid.   The solid-state light-emitting device is at least one of a light-emitting diode, a semiconductor laser, a laser diode, and an AlyInxGa1-y-xN (0 ≦ y ≦ 1; 0 ≦ x ≦ 1; 1-yx ≧ 0) semiconductor material. The sensor of any one of Claims 1-7 characterized by including one.   The sensor according to claim 1, further comprising a stabilization device that stabilizes the wavelength of light emitted from the solid state light emitting device.   The stabilizing device includes a diffraction grating, a dichroic mirror, a temperature control device that adjusts the temperature of the solid state light emitting device, a wavelength filter, a current regulator that adjusts the current supplied to the solid state light emitting device, and the solid state light emission. The sensor according to claim 9, comprising at least one voltage regulator for regulating the voltage supplied to the device.   11. The sensor according to claim 1, further comprising a wavelength sensor that outputs data indicating a wavelength of light emitted from the first light source.   12. The wavelength sensor includes at least one of a temperature sensor that measures a temperature of the first light source, a current sensor that measures a current supplied to the first light source, and a spectrophotometer. Sensor. Said frequency conversion element, the β-BaB ₂ O _{4 crystal, Ba 1-x B 2-} yz O 4 - Si x Al y Ga z (0 ≦ x ≦ 0.15; 0 ≦ y ≦ 0.10; 0 ≦ z ≦ 0.04 x + y + z ≠ 0; 2-yz ≧ 0), SiO ₂ , Al _y Ga _1-y N (0.5 ≦ y ≦ 1), CsLiB ₆ O ₁₀ , LiB ₃ O ₅ , KBe ₂ BO ₃ F ₂ The sensor according to claim 1, comprising Li ₂ B ₄ O ₇ , LiRbB ₄ O ₇ , or MgBaF ₄ .   The first light source emits light having a first center wavelength emitted from the solid-state light emitting device, and light having a second center wavelength different from the first center wavelength, which is frequency-converted, in the fluid. The concentration of one or more kinds of ions, molecules, or atoms is based on the transmittance of light having the first central wavelength and the transmittance of light having the second central wavelength. The sensor of any one of -13. The first light source, which operates in at least two operating conditions, the second wavelength intensity of light of the first wavelength emitted from the P _a from the first light source, a P _b emitted from the first light source The sensor according to claim 14, wherein the ratio P _a / P _b is different under the at least two operating conditions.   The sensor according to claim 1, wherein the first light source emits light having a spectral bandwidth of less than 2 nm (nanometers).   The absorbance of the light emitted from the first light source by one or more types of ions, molecules, or atoms in the fluid is substantially equal to the concentration of the one or more types of ions, molecules, or atoms in the fluid. The sensor according to claim 1, wherein the sensor has a linear dependence relationship.   The sensor according to claim 1, wherein the at least one fluid contains substantially water or ions containing nitrate ions. A system for monitoring the concentration of one or more ions, molecules or atoms in a fluid,
The sensor according to any one of claims 1 to 18,
A warning device that operates in connection with the sensor; and at least one of a concentration variation device that operates in connection with a controller that operates in connection with the sensor; and
The warning device generates an output indicating that the concentration of one or more types of ions, molecules, or atoms in the fluid is outside a specified concentration;
The concentration varying device varies the concentration of one or more types of ions, molecules, or atoms in the fluid, and the controller controls the operation of the concentration varying device based on data from the sensor. Feature system.